
Glass. 



Book. 



THE EDWIN C. DINWIDDIE 

COLLECTION OF BOOKS ON 

TEMPERANCE AND ALLIED SUBJECTS 



(PRESENTED BY MRS. DINWIDDIE) 






• 






Springfield* Q* 





THE LARGEST TELESCOPES IN THE WORLD 

Lord Rosse's Telescope, at Birr Castle, Ireland, 56 feetin length. 

Silt Win. Hersohei/s do. at Greenwich, London, 40 do. in length (not in use ) 

The Dorpat Telescope, at Dorpat (Russia,) Prof. Striate, 16 " 

Sir James South 's Telescope at London, 19 " 

Cincinnati Telescope, (Ohio,) Prof. Mitchel, 17 " 

Telescope at Cambridge, Mass 23 



HINTS TO TEACHERS. 



The author would recommend that whenever a lesson is, given to a class, that the 
teacher call their particular attention to the illustration, and explain, if necessary, the 
diagrams relating to the lesson given, at the same time questioning the whole class 
upon the subject; and inviting any pupil who does not fully understand the subject to 
ask any questions relating to it he may think proper. This will prepare the pupil, when 
he is studying his lesson, to have a right conception of what he is learning. It is not 
expected by the author that the teacher will confine himself solely to the que** ; ons 
given in the book ; but that he will ask many which may occur to him at that time, ana 
which n ay lead the pupil off from the routine of the book, and induce him to apply the 
principles wliich he is endeavoring to acquire 



He would also particularly recommend, that the teacher when hearing a recitation, 
change the question or put it in a different form, in all cases where it will admit ot it. 
For example : , , 

What is the attraction, by which all particles of matter tend toward each other. 
called 1 The attraction of gravitation. . „ . . , 

What is the attraction of gravitation 1 It is that attraction by which all particles ot 
mattpr tend toward each other. 

What is the point in the heavens directly over our heads called 1 Ihe zenitn. 

What is .he zenith 1 It is that point in the heavens directly over our neaas. 






^REVISED AND ENLARGED.) 



S MI T H'S 



ILLUSTRATED 



ASTRO 










DESIGNED FOR THE USE OF THE 



PUBLIC OR COMMON SCHOOLS 



II THE UNITED STATES 



ILLUSTRATED WITH 



UMEROUS ORIGINAL DIAGRAMS 



BY ASA SMITH, 

Principal of Public School No.' 12, City of New York. 



FIFTEENTH EDITION. 



Nero- j) or k: 
DANIEL BURGESS & CO,, 60 JOHN-STREET. 

(LATE CADT & BURGESS.) 

185 5. 



ILLUSTRATED ASTRONOMY. 



CONTENTS, 



Lesson. Page. 

1. Vague ideas of the Ancients respecting the Shape of the Earth, - 7 
" Ptolemaic System, ...... 7 

2, 3. Introduction to Astronomy, - - - - - 7 
4, 5, 6. Astronomy, Solar System, &c. .... 9 

7. Diameters, Magnitudes, Distances and Revolutions of the Sun and 

Planets, ....... 9 

8. Centripetal and Centrifugal Forces, - - - - - 1 1 

9. Kepler's Laws, - - - - - - -11 

" Mean and True Place of a Planet — Aphelion and Perihelion, - - 11 

10. Mean and True Motion of a Planet, - - - 11 

11, 12. The Sun; Spots on the Sun, - - - - - 13 

13. Transits of Mercury and Venus, - - - 13 

14. Zodiac; Constellations of the Zodiac, - - - - 15 

15. Apparent Motion of the Sun in the Heavens, - - 15 

16. Signs of the Ecliptic, &c. - - - - - - 15 

17. The Planet Mercury, - - - - - 17 

18. The Planet Venus, - - - - - - - 17 

19. Seasons at Venus, Phases, &c. - - - - 17 

20. 21, 22. Earth, Definitions, &c. - - - - - 19 

23, 24, 25. Earth and Seasons, Equinoxes, &c. ... 21 

— Aerolites, Meteors, &c. - - - - - - 23 

26, 27. Mars, Asteroids, - - - - - 25 

28, Jupiter, Saturn's Rings, - - - -• - - 27 

29, 30. The Planet Saturn, ...... 29 

31. The Planet Herschel, or Uranus, - - - - - 31 

32. The Planet Leverrier, or Neptune, • - - - 3 1 

33. The Moon ; Phases of the Moon, - - - - - 33 



-Physical Constitution of the Moon, - 



Lesson. 

34, 35. The Moon— (continued) 

36. Eclipses, 

37, 38, Moon's Nodes, Inferior and Superior Conjunction, 

39. Inferior and Superior Planets, 

40. Greatest Number of Eclipses in a year, 

41. 42. Tides, ----- 
43, 44. Orbits of the Planets and Comets ; Comets, 

45. Atmosphere, ....... 

46. Refraction, - - - - 
47- Parallax, -------- 

48. Light and Heat, ------- 

49. Terrestrial and Celestial Globes, - 

50. 51. General Definitions respecting the Globes, ... 

52. Fixed Stars ; Distance to the nearest Fixed Star, - 

53. Our own Cluster or Firmament of Stars, Motions of the Stars, Multiple 

Stars, Binary Systems, ------ 

Nebuls, Number, Distance, &c. ; Origin of the Solar System, 

An Explanation of Leap Year, - - . . . 

Equation of Time, ...... 

To find the Magnitudes of the Planets, - . . . 

To find the distances of the Planets from the Sun, - - - 

Zodiacal Light, ....... 

To find the circumference of the Earth, .... 

Problems on the Terrestrial Globe, - . . . . 

Problems on the Celestial Globe, ----- 

Glossary or Explanation of Astronomical Terms, 



Tage. 

35 

38-40 

42 

- 42 
44 

- 46 
48-50 

- 52 



54 



52 

52 
52 
54 
54 
56 

- 56 
58 

- 64 
64 

- 68 
68 

- 72 
72 

- 76 
77 

78-79 



ILLUSTRATIONS. 



Orrery, with a view of the Solar System in the back ground, - - 6 

Solar System and Comparative Magnitudes, ... 8 

Centripetal and Centrifugal force, - - - - 1 

Kepler's Laws, - - - - - -10 

The Mean and True Place of a Planet, - - - - 10 

Circle; Eclipse; Concentric Circles ; Circles not in the same plane, - 10 

Cut Section of the Sun, - - - - - 12 

Spots on the Sun, - - - - 12 

Transits to the year 1900, - - - - - 12 

Signs of the Zodiac, - - - - - 14 

Mercury and Venus ; Telescopic Views ; Venus Morning and Evening Star, 16 

Earth and Definitions, - - - - - 18 

Seasons ; Summer and Winter Rays, Equinoctial and Solstitial Points, - 20 

Aerolites and Meteors, ----- 22 

Mars, Asteroids and Jupiter, - • • - - 24 

Jupiter ; Telescopic Views, &c. - - - - 26 

Saturn ; Saturn's Rings and Moons, - - - - 28 



Herschel and Leverrier, - 

Phases of the Moon ; Apparent Magnitude of the Sun and Moon, 

Telescopic View of the New Moon, - - - - 

Telescopic View of the Full Moon, - 

Telescopic View of the Old Moon, - 

Eclipses, - 

Moon's Nodes ; Inferior and Superior Conjunction, 

Inferior and Superior Planets ; Heliocentric Longitude, 

Greatest Number of Eclipses that can happen in a year, 

Tides, and Moon-light at the Poles, - 

Orbits of the Planets and Comets ; Comets, - 

Refraction ; Parallax Light and Heat, 

View of the Earth's Orbit, as seen from the nearest fixed Star, 

Terrestrial and Celestial Globes, and Milky-way, 

Binary Systems ; Quadruple Stars, - - - - 

A Perpendicular and an Oblique View of our own Cluster or Firmament, 

Telescopic Views of remarkable Nebulae and Cluster of Stars, - 



30 

- 32 
34 

- 36 
37 

39-41 
43 

- 43 
45 
47 

-51 
53 
53 
55 
57 
57 
59 



49 



SIDEREAL MAPS, 



Description and use of the Sidereal Maps, - - - 60 

Explanations, showing the manner of using the Maps, - 60 

Directions for finding the North Star at any time, - - 60 

Description of the Constellations visible from January 21st to April 17th, 61 
Principal Stars visible, and Times for Observation, from January 21st to 

April 17th, - - - -62 

Map of the Visible Heavens, from January 21st to April 17th - 63 

Descriptions of the Constellations visible from April 18th to July 21st. 65 

Principal Stars visible, and Times for Observation, from April 18th to July 21st. 66 



Map of the Visible Heavens, from April 18th to July 21st. - 

Descriptions of the Constellations visible, from July 22d to October 31st. 

Principal Stars visible, and Times for Observation, from July 22d to Octo- 
ber 31st. - - . . 

Map of the Visible Heavens, from July 22d to October 31st. - 

Descriptions of the Constellations visible, from November 1st to January 20th. 

Principal Stars visible, and Times for Observation, from November 1st to 
January 20th. - . - 

Map of the Visible Heavens, from November 1st to January 20th. 



Entered according to Act of Congress, in the year 1S49, by Aa± Shiti 



mith, in the Clerk's Office of the District Court of the United States, for the Southern- District of New York. 



67 
69 

70 
71 
73 

74 
75 



Bterhottpid bt 

VINCENT L. DILL, 

128 Fullon Street, N. T 



$EP'a> 



-con 



*M Yl 



Gift 
Edwii C D nwiddie 



C. A. AITOSD, PK1SIIE 



Aug. £■ 1?35 



PREFACE 



TO THE REVISED EDITION. 



Nearly six yeare have elapsed since the publication of this Illustrated Astronomy ; during this time many new planets or Asteroids have been 
discovered ; a notice of which will be found in its proper place ; also a notice of Professor Bond's new theory in regard to Saturn's rings. 

The favor with which this work has been received by teachers and the public generally has far exceeded the author's expectations, it having run 
through fifteen Editions since its publication. It has been thoroughly revised, and the new discoveries are brought up tothe present date; five new 
illustrations have been added and a new set of Electrotype plates have been procured at a great expense, which give a very distinct and beautiful diagram. 

It has been the object of the author of this Illustrated Astronomy, to present all the distinguishing principles in physical Astronomy with as 
few words as possible ; but with such occular demonstrations, by way of diagrams and maps, as shall make the subject easily understood. The 
letter press descriptions and the illustrations will invariably be found at the same opening of the book ; and more explanatory cuts are given, and at a 
much less price than have been given in any other elementary Astronomy. 

This work is designed for common schools, but may be used with advantage as an introductory work in high-schools and academies. In the prepa- 
ration of these pages most of the best works in our language have been consulted, and the best standard authorities, with regard to new discoveries 
and facts, have governed the author's decisions. 

The Diagrams, which are larger and more full than those of any other work adapted to common schools, are most of them original in their 
design, and exhibit the positions and phases of the planets in their orbits. The drawings being upon the principal of perspective, exhibit the in- 
clinations of their several axes to the planes of their orbits more correctly than has hitherto been done in any other popular work. It is well to 
intimate to the young elementary student, who has made himself some what acquainted with the sublime mechanism of the solar system, that 
there is something more magnificent beyond. Accordingly the author has given a few Sidereal Maps, just to awaken in the young astronomer the 
amazing conception, that unnumbered suns and revolving worlds occupy the depths of space far beyond the confines of our planetary system. By 
these maps he will be able to learn the relative positions of the principal constellations and stars, which will be found useful and interesting to him 
in subsequent investigations of the ennobling truths of mathematical Astronomy. 

The author is not so vain as to suppose that he has been able to present to teachers a faultless work ; but in his own practice, finding it tedious 
and often difficult to explain all the representable phenomena of the science on the black-board, and finding also a general concurrence of opinion 
among teachers most interested in the study of Astronomy, that a cheap, compact, and illustrated work is necessary in our common schools, he has 
attempted the production of such a work. The success of the work and the favor with which it has been received, sufficiently prove its superiority over 
all other works for the instruction of pupils in the general outlines of the science of Astronomy, and satisfies the author that he has not labored in 
vain in the production of this work. 

Objections which are sometimes urged against questions and answers, in an elementary work, will not, the Author hopes, be urged in this case, as 
the pupil has the subject, fully illustrated, continually before the eye, while he is learning his lesson. 

To the Teachers, of our common country, this work is most respectfully dedicated, in the sincere desire that the cause of education may be 
benefitted, and the labors of instruction in Astronomy may be rendered more easy and pleasant, from the illustrations it contains. 

ASA SMITH, Principal of Ward School No. 11, [Late Public School, No. 12,) 

Seventeenth Street, near Eighth Avenue, City of New York. 



NAMES AND CHARACTERS OF THE SIGNS, PLANETS, AND ASPECTS. 



Aries, 

Taurus, 

Gemini, 

Cancer, 

Leo, - 

Virgo, 

Libra, 

Scorpio, 



T Sagittarius - - $ Earth, - - © 

y Capricornus, - VJ ' Mars, • - $ 

EI Aquarius, - - £2 Vesta, - - ' fi 

52 Pisces, - - ^ Juno, - - 

S\ Sun, - - © or O Ceres, - - •? 

n# Moon, ® O © ® Pallas, - - $ 

£z Mercury, - - 5 Astrasa,* 

Til Venus, - - § Flora* - 

* Not determined. 



Hebe* - ■ 

Iris* 

Jupiter, 

Saturn, 

Herschel, 

Leverrier, - 

Conjunction, 

Sextile, 



h 
W 

6 

* 



Quartile, 
Trine, - " - 
Opposition, - 
Ascending Node, 
Descending Node, 



□ 

A 

<? 



The following is a list of the names of the new Asteroids, date of discovery, and by whom discovered, 



Name and Number. 



1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 
10. 
11. 
12. 



Ceres 

Pallas 

Juno , 

Vesta , 

Astrsea , 

Hebe , 

Iris 

Flora 

Metis 

Hvgeia 

Parthenope.. . 
Victoria 



Date of Discovery 



1800, 
1802, 
1804, 
1807, 
1845, 
1847, 
1847, 
1847, 
1848, 
1849, 
1850, 
1850. 



Jan. 

Mar. 

Sept 

Mar. 

Dec. 

July 

Aug 

Oct. 

Apri 

Apri 

May 

Sept 



1. 

28. 
. 1. 

29. 

8. 

1. 
. 13. 

18. 
1 26. 
12. 

11. 

13. 



Name of Discoverer. 



Piazza, of Sicily. 

Olbers, of Bremen. 

Harding. 

Olbers. 

Hencke, of Germany. 

Hencke. 

Hind, of London. 

Hind. 

Graham, of Ireland. 

De Gasparis, of Naples. 

De Gasparis. 

Hind. 



Name and Number. 



13. Egeria 

14. Irene 

15. Eunomia. . . . 

16. Psyche 

17. Thetis 

18. Melpomene... 

19. Fortuna 

20. Massilia... . . 

21. Lutetia 

22. Calliope 

23. Thalia .. 



Date of Discovery 



1850, 
1851, 
1851, 
1852, 
1852, 
1852, 
1852, 
1852, 
1852, 
1852, 
1852, 



Nov. 2. 
May 19. 
July 29. 
Mar. 17. 
April 17. 
June 24. 
Aug. 22. 
Sept. 22. 
Nov. 15. 
Nov. 16. 
Dec. 15. 



Name of Discoverer. 



De Gasparis. 

Hind. 

De Gasparis. 

De Gasparis. 

Luther, of Germany. 

Hind. 

Hind. 

De Gasparis. 

Goldschmidt, of Germany. 

Hind. 

Hind. 



INTRODUCTION TO ASTRONOMY. 



LESSON I. 

Question. What is the body called upon which we live? 

Answer. It is called the Earth, or World. 

Q. What idea had the Ancients respecting the shape of the earth ? 
A. They believed it was an extensive plain, rendered 
uneven by hills and mountains. 

Q. Why did they think it was an extended plain ? 
A. Because they formed their opinions from appear- 
ances only. 

Q. Did they believe that the earth had any motion ? 
A. They did not ; they believed that the earth rested 
on a solid, immovable foundation. 

[They very naturally came to this conclusion, as they were entirely; ignorant of the laws of 
attraction or gravitation. They believed that if the earth were to turn over, that every thing 
would be precipitated from its surface] 

Q. Had they any definite ideas respecting what held the earth up ? 
A. Their views were very vague and unsatisfactory. 

[There have been many absurd ideas advanced, at different ages of the world, as to what sup- 
ported the earth. Some supposed it to be shaped like a Can'Ok, and to float upon the waters ; o'hers, 
that it rested upon the back of an Elephant, or huge Turtle ; while, according to mythology, 
Atlas supported it upon his shoulders : but, what kept the waters in their place, or upon what the 
Elephant. Turtle, or Atlas stood — this was a mystery they could never solve.] 

Q. Did they believe the earth extended the same distance in all 
directions ? 

A. They believed it to extend much farther from east 
to west than from north to south. 

[They observed that in going east or west, on the same parallel of latitude, no change took 
place in the appearance of the heavens ; but in gning north or south, on the same meridian, every 
sixty miles caused a difference of one degree in the elevation of the pole and in the position of the 
circles of daily motion of the sun and other heavenly bodies ; therefore they concluded that the 
earth was very long from east to west, but comparatively narrow from north to south. From this 
originated the use of the terms longitude and latitude ; longitude meaning length, and latitude, 
breadth ] 

.. Q. What ideas had they respecting the motions of the sun, moon, 
and Stars ? 

A. They supposed that they revolved around the 
earth, from east to west, every day. 

Q. What, was this system called, th'at supposed the earth to be at 
rest in the centre, and all the heavenly bodies to revolve around it? 

A. The Ptolemaic system. 

[Ptolemy asserted, that the sun. moon, planets, and stars revolved around the earth, from east to 
west, every '24 hours ; and to account for their not falling upon the earth, when they passed over 
it. he supposed that they were each fixed in a separate hollow crystalline globe, one within the 
other. Thus the moon was in the first ; Mercury in the second ; Venus in the third ; the sun in 
the fourth ; Mars in the fifth ; Jupiter in the sixth : Saturn in the seventh ; — (the planet Herschel 
was not known at this time) — the fixed stars in the eighth. He supposed the stars to be in one 
sphere as they are kept in the same positions with respect to each other. To permit the light of 
the stars to pass down to the earth, he supposed these spheres or globes were perfectly clear or 
transparent like glass The power which moved these spheres, he supposed, was communicated 
from above the sphere which contained the stars ] 



LESSON II. 

Question. Every one is conscious that the sun, which rises daily in 
the east and sets in the west, is the same- body ; where does it go 
during the niffht ? 

Answer. It appears to pass round under the earth. 

Q. When we look out upon the stars, on successive evenings, they 
appear to have a definite position with respect to each other, and a 
westward movement like the sun ; what motion do they appear to have 
from their setting to their rising ? 

A. They appear to pass under the earth. 

Q. From the north to the south point of the heavens, there is a con- 
tinuous arc of stars, and in their passage under the earth they are not 
at all disarranged, what can you infer from this fact? 

A. That they pass completely around the earth, and 
every thing attached to it. 



Q. We see no body at rest that does not touch some permanent sup- 
port, but we see bodies in motion supported for different lengths of time 
without resting upon any other surface ; if the earth is hung upon 
nothing, is it probably at rest ? 

A. It is more probable that it is in motion. 

Q. If we throw a ball, does the same side always remain forward? 
A. It does not; it turns over continuously. 

Q. What do we call the line round which it turns ? 
A. Its axis. 

Q. If a fly were on the ball, would distant objects appear to him to 

be stationary? 

A. They would appear to revolve around the ball, as 
often as it turned over. 

Q. If the earth is moving in space, is it in accordance with the 
known motion of ordinary bodies, to suppose that the same side 
remains forward ? 

A. It is not. It is more reasonable to suppose that it 
turns on its axis. 

Q. If the earth turns, and we are carried round on its surface, what 
appearance must the sun and distant stars necessarily present ? 

A. They must appear to move around the earth in the 
opposite direction. 



LESSON III. 

Question. What other reason can )-ou give for the earth's turning ? 

Answer. The stars are so distant, that their motion 
would be immensely swift, in comparison with the mo- 
tion of the earth, to produce the same effect. 

Q. But have we not positive proof, and that too of different kinds, 
that the earth turns on its axis ? 

A. We have. — 1. The shape of the earth, elevated at 
the equator and depressed at the poles, can be ac- 
counted for on no other supposition. 

2. A body at the equator, dropped from a great 
height, falls eastward of the perpendicular. 

3. The trade winds and ocean currents in the tropi- 
cal regions are clearly traceable to the same cause. 

Q. If the earth is moving in space, does it proceed in a straight 
line ? 

A. It does not ; but it would do so, were it not 
attracted by other bodies. 

Q. What is the attraction, by which all particles of matter tend 
towards each other, called ? 

A. The attraction of gravitation. 

Q. What large body, by its attraction, causes the earth to revolve 
around it in a curve line ? 

A. The sun. 

Q. What other similar bodies revolve around the sun ? 

A. The planets. 

Q. What may we call the earth, when considered with regard to its 
size, shape, motions, &c. ? 
A. One of the planets. 

Q. What science describes these characteristics of the earth, and 
other heavenly bodies ? 

A. Astronomy. 



ILLUSTRATED ASTRONOMY 



LESSON IV. 
ASTRONOMY. 

Question. What is astronomy 1 

Answer. Astronomy is the science which treats of the 
heavenly bodies. 

Q. What arc the heavenly bodies ? 

A. The sun, moon, planets, comets, and stars, 

Q. What are some of their characteristics, of which astronomy treats ? 
A.. Their appearance, size, shape, arrangement, dis- 
tance, motions, physical constitution, mutual influence 
on each other, &c. 

Q. Are they all of the same magnitude, or size? 

A. The sun and stars are much larger than the other 
bodies. 

Q. Are they all at the same distance from the earth ? 

A. They are not ; the moon is the nearest, and the 
stars the most distant. 

Q. Do they all emit light of themselves** 

A. They do not. 

Q. How are they divided in this respect? 

A. They are divided into -two classes, luminous and 
opake. 

Q. What is a luminous body? 

A. It is a body which shines by its own light. 

Q. What is an opake body ? 

A. it is a body which shines only by reflecting the 
hjhl of a luminous body. 

Q. Which are the luminous bodies in the heavens? 

A. The sun and fixed stars are luminous bodies. 

Q. Which are the opake bodies in the heavens ? 
A. The moon, planets, and comets. 

Q. Why do the moon, planets, and comets appear luminous? 

A. Because they reflect to us the light of the sun. 
Q. What is the shape of the heavenly bodies ? 
A. They are round like a globe or ball. 
Q. What do the sun, moon, planets, and comets constitute ? 
A. They constitute the solar system. 

LESSON V. 
THE SOLAR SYSTEM. 

Question. How are the bodies constituting the solar system arranged ? 

Answer. The sun is placed in- the centre of the sys- 
tem, with the planets and comets revolving around it 
at unequal distances. 

Q. How many planets are there in the solar system ? 

A. Fifty-two is the number known at present. 

Q. How are they divided with respect to their motion ? 

A. They are divided into two classes, primary and 
secondary. 

Q. What is a primary planet? 

A. It is a planet which revolves around the sun only. 

Q. What is a secondary planet ? 

A. It is a planet which revolves around its primary, 
and with it around the sun. 

Q. What are the secondary planets usually called ? 

A. They are called satellites or moons. 

Q. How many primary planets are there ? 

A. 8 large planets and 23 asteroids or small planets. 



Q. What are their names, beginning at the sun ? 

A. Mercury, Venus, the Earth, Mars, (Twenty-three 
Asteroids or small Planets,) Jupiter, Saturn, Herschel, 
or Uranus, and Leverrier, or Neptune. 

Q. How many secondary planets or moons are there ? 

A. Twenty-one. 

Q. Which planets have moons ? 

A. The Earth has 1, Jupiter 4, Saturn 8, Herschel 
6, and Leverrier 2. . 



LESSON VI. 

Question. How many revolutions has a primary planet? 

Answer. Two; one on its axis, and another around 
the sun. 

Q. What is the axis of a planet ? 

A. It is a straight line, round which it turns. 

Q. What is the path called, in which a planet revolves around the sun ? 

A. It is called its orbit. 

Q. What is the earth's orbit called?. 
A. It is called the ecliptic. 
Q. Why is it so called ? 

A. Because eclipses take place, only when the moon 
is in its plane. 

Q. How many revolutions has a secondary planet ? 
A. Three. 1st, the revolution upon its axis ; 2d, the 
revolution around its primary ; 3d, the revolution with 
its primary around the sun. 

Q. How are the planets divided, with respect to their distance from 
the sun ? 

A. Into inferior and superior, according as their dis- 
tance from the sun is inferior or superior to that of the 
earth. 

Q. Which are the inferior planets? 

A. Mercury and Venus. 

Q. Which are the superior? 

A. Mars, the Asteroids, Jupiter, Saturn, Herschel, 
and Leverrier. 



LESSON VII 



DIAMETERS. 


Magnitudes ; 
the Earth 

BEING 1. 


Distances from 
the Sun. 




Miles. 




Miles. 


Sun, 


886,952 


1,384.472 




Mercury, 


3.200 




37,000,000 


Venus, 


7,700 


9 


68,000,000 


Earth, 


7.912 


1 


95,000,000 


Mars, 


4,189 


i 


142,000,000 


Vesta, 


270 


! 
# • * 2$TffO 


225,000,000 


Astrosa, unknown. 


Unknown. 


253,000,000 


Juno, 


1.400 


i 


254.000,000 


Ceres, 


1,600 


i 


263,000,000 


Pallas,* 


2,100 


i 


263,000,000 


Hebe, unknown. 


Unknown. 


Unknown. 


Iris, 


u 


a 


u 


Flora, 


u 


n 


u 


Jupiter, 


87,000 


1,280 


485,000,000 


Saturn, 


79,000 


1,000 


800,000,000 


Herschel, 


35,000 


80 


1,800,000,000 


Leverrier 


35,000 


SO 


2,850,000,000 



Revolution 


Revolution 


ON 


AROUND 


THEIR AXIS. 


THE 


Sun-. 


Days. Hours. 


Years. 


Days. 


25 10 






24 




88 


2'S-h 




224 


24 


l 





24^ 


l 


321 


Unknown. 


3 


230 


M 


4 


105 


, it 


4 


131 




4 


222 


a 
u 

10 


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diameter of each of the asteroids to be under 200 miles. Their great dis 
and nebulous appearance, render it extremely difficult to ascertain their 




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ILLUSTRATED ASTRONOMY, 



11 



! 



LESSON VIII. 

CENTRIPETAL AND CENTRIFUGAL FORCE. 

Question. What is that force called with which all bodies attract 
each other in proportion to their mass ? 

Answer. The attraction of gravitation. 

Q. What is centripetal foice ? 

A. It. is the force which draws a body towards the 
centre round which it is revolving. 

Q. What targe body by its attraction exerts a centripetal force upon 
all the primary planets and comets ? 

A. The sun. 

Q. What body exerts a centripetal force upon the moon ? 

A. The earth. 

Q. What bodies exert a centripetal force upon the other moons ? 

A. The primary planets around which they revolve. 

Q. What is the centrifugal force of a heavenly body? 

A. It is that force which moves it forward in its orbit. 

Q. How do these two forces cause the planets to move ? 

A. They cause them to move in circular or elliptical 

orbits. 

Q. What is a circle ? 

A. It is a plane figure bounded by a curve line, all parts 
of which are equally distant from the centre. — (Fig. 4.) 

Q. What is an ellipse ? 

A. It is an oblique view of a circle. (Fig. 4.) 

(Note. — Teachers should tie sirre-that the pupils understand the definition of an ellipse, because 
in viewing some of the diagrams tiiey may receive a wrong impression. In the diagram repre- 
senting the seasons, i!:e earth's orbit appears very elliptical : this Mould be well understood by the 
i'Mt il, should the teacher call his particular attention to it. Also, a plane of a circle should he well 
understood.] 

Q. What are the foci of an ellipse? 

A. They are the two points around which the ellipse 
is drawn. (Fig. 7.) 

Q Where are these points situated ? 

.4. In the greater axis, at equal distances from the 
centre. 

('/. What is the eccentricity of an ellipse? 

A. It is the distance from the centre to either of the 
foci. (Fig. 7.) 

Q, Where is the sun situated within the orbit of each planet? 

A. It, is situated in one of the foci. (Fig. 8.) 

Q. When are circles in the same plane? (Fig. 5.) 

A. When their planes lie in the same straight line. 

Q. When are circles not in the same or parallel planes? 

A. When their planes intersect each other. (Fig. 6.) 
LESSON IX. 

Question. How many laws did Kepler discover, which bear his name? 

Answer. Three. 

(>. To what do they relate ? 

A. They relate to the motions of the planets. 

Q. What is the first law of Kepler? 

A. That all the planets revolve in elliptical orbits, 
having the sun in one of their foci. (Fig. 7.) 

Q. What is the second law ? 

A. That the radius vector passes over equal spaces in 
equal portions of time. 

Q. What is the radius vector ? 

A. It is a line drawn from the sun to a planet, in any 
part of its orbit. (Fig. 7.) 

Q. What is the third law ? 

A. It is that the squares of the times of the revolu- 
tions of the planets around the sun, are proportional to 
the cubes of their mean distances from the sun. 



THE MEAN AND TRUE PLACE OP A PLANET. 

Q. What is the mean place of the earth, or a planet in its orbit? 
A. It is that point in its orbit where it would be if it 
moved in a circle, and with the same velocity at all 
times. (Fig. 8.) 

Q. What is the true place of the earth or a planet ? 

A. It is that point in its orbit where it really is at any 
given time. (Fig. 8.) 

Q. What is the aphelion ? 

A. It is that point in the orbit of the earth or planet 
farthest from the sun. (Fig. 8.) 

Q. When is the earth in the aphelion, or farthest from the sun ? 

A. July 1st. (Fig. 8.) 

Q. What is the perihelion? 

A. It is that point in the orbit of the earth or planet 
nearest to the sun. (Fig. 8.) 

Q. When is the earth in the perihelion, or nearest to the sun? , 

A. January 1st. (Fig. 8.) 



LESSON X. 

Question. In what points of a planet's orbit do its mean and true 
places coincide ? 

Answer. At the aphelion and perihelion. (See Fig. 8.) 

f L >. What straight line connects these points, and passes through the 
sun ? 

A. The apsis line. 

Q. When is the true place of the earth or planet behind its mean 
place? 

A. While it is moving from the aphelion to the peri- 
helion. (See Fig. 8.) 

Q. When is the true place of the earth or planet before its- mean 
place ? 

A. While it is moving from the perihelion to the 
aphelion? (See Fig. 8.) 

Q. When does it move with the least velocity? 
A. When it is at its greatest distance from the sun. 

Q. W T hen is the motion of the earth or planet in its orbit increasing? 
A. When it is moving from the aphelion to the peri- 
helion. 

Q. Why does the motion increase from the aphelion to the perihelion ? 
A. Because it is approaching nearer to the sun. 

Q. What causes it to approach the sun ? 

A. The centrifugal force at the aphelion is not suffi- 
ciently great to prevent its falling towards the sun. 

<','. When does the earth or planet move with the greatest velocity? 
A. When it is the nearest to the sun. 

Q. When is the motion of the earth or planet decreasing ? 

A. While it is moving from the perihelion to the 
aphelion. 

Q. Why does the motion decrease from the perihelion to the aphelion ? 
A. Because the planet is receding from the sun. 

Q. What causes it. to recede from the sun ? 

A. The centrifugal force at the perihelion is so great 
as to carry it farther from the sun. 

CENTRIPETAL AND CENTRIFUGAL FORCES. 

A body projected by any force would always move forward in a straight line, and with the same 
velocity, unless acted upon hy some other force. A hall discharged from a gun or thrown front the 
linn, I soon looses its projectile force hy the resistance of the atmosphere, and is brought to the 
ground by the attraction of the earth, or ce*ntnpetal force (f"i<, 3 ) These two forces can he well 
illustraied. "(See Fir.. 1. Q.) by tying a string to a hall and swinging it round ; the centrifugal k-rce 
imparted to the ball by the hand and by means of.the string, causes the ball to move in a circle ; hut 
if the string should break, the centrifugal force would carry it oil' in a straight line, if the ball were 
not attracted by the earth. The string corresponds to the attraction of the s,im in our solar sys- 
tem, which causes the planets to move in regular curves around the sun, instead of straight hue 
If the attraction of the sun or centripetal force should cease, the planets would fly oft" into space 
in straight lines ; but if the centrifugal force should cease and the centripetal force continue, the 
planets would immediately fad into the sun 



?2 



A CUT SECTION OF THE SUN 

SHOWING THE SPOTS,THE LUMJNOUS ATMOSPHERE, 
AND THE OPAKE BODY OF THE SUN. 



SPOTS ON THE SUN 



NORTH 





SOUTH 






REMARKABLE SPOTS THAT HAVE 
BEEN DISCOVERED UPON THE SUN 



TRANSITS of MERCURY & VENUS UNTIL THE 

YEAR 1900 



NORTH 




ILLUSTRATED ASTRONOMY 



13 



LESSON XI. 
THE SUN. 

Question. What body is in the centre of the solar system? 

Answer. The sun. 

Q. Describe the sun ? 

A. The sun is a large luminous body, which gives 
light and heat to the whole solar system. 

Q. What is the diameter of the sun ? 

A. 886,952 miles. 

Q. How much larger is the sun than the earth ? 

A. It is 1,384,472 times greater. 

Q. What is the specific gravity of the sun ? 

A. It is lh the weight of water. (1.38.) 

Q. What is the size of the sun compared with the planets ? 
A. It is 500 times as great as the bulk of all the 
planets. 

Q. What can you say of its mass or weight ? 

A. It is about 750 times the mass of all the planets. 

Q. What is the distance of the sun from the earth ? 

It is about 95,000,000 of miles. 

What did the ancient astronomers consider the sun to be ? 



A. 

Q. 

A. 

Q. 



A large globe of fire. 



What do astronomers at the present day consider it to be ? 

A. An opake body like the earth, surrounded by a 
luminous atmosphere. 

Q. What motions has the sun ? 

A. It has three motions— ^-Ist, on its axis ; 2d, around 
the centre of gravity of the solar system ; 3d, around 
the centre of the universe. 

[The term universe is used by astronomers, though perhaps improperly, to designate the great 
cluster or firmament of stars in which our sun is situated.— (See pages 45 and 46.) This cluster 
includes all the single stars that can be seen with the naked eye, and all those composing the galaxy 
or milky way. The number of stars or suns in the cluster i& estimated at many millions ; all which, 
like our sun, are supposed to revolve around the common centre of gravity of the whole cluster. 
Several thousand other distinct cluster's or nebulas, situated without our firmament, can be seen by 
the best telescopes, nearly all of which are invisible to the unassisted eye.] 

LESSON XII. 

Question. What is the inclination of the sun's axis to that of the 
ecliptic ? 

Answer. About Ik degrees. 

Q. In what time does it revolve on its axis 1 

A. In about 25 days and a half. 

Q. How is the revolution of the sun on its axis determined ? 

A. By spots on its surface, which first appear on the 
east side, pass oyer, and disappear on the west side. 

Q. What is the nature of these spots? 

A. They are supposed to be openings in the luminous 
atmosphere, which enable us to see the dark body of 
the sun. 

Q. What occasions these openings in the luminous atmosphere? 

A. They have been attributed to storms and various 
other causes. 

Q. Do these spots undergo any changes ? 

A. They are constantly changing, and sometimes very 
rapidly. Some have appeared, others disappeared sud- 
denly. 

Q. On wbat part of the sun do they appear? 

A. Within about thirty degrees of the equator. 

Q. Is the surface of the sun, in the region of the spots, tranquil or 
agitated ? 

A. It is in a state of continual and violent agitation. 



Q. What reasons have we to suppose that the luminous part of the 
sun is intensely hot ? 

A. 1st, the heat of its rays, when collected into a 
focus, is very great. 2d, its rays pass through glass 
with the greatest facility, (a property belonging to arti- 
ficial heat in direct proportion to its intensity.) 3d, the 
brightness of the sun is greater than the most vivid 
flames, or the most intensely ignited solids. 

LESSON XIII. 

TRANSIT OF MERCURY AND VENUS. 

Question. What is the transit of a heavenly body ? 

Answer. It is its passage across the meridian. 

Q. What is generally meant by the transit of Mercury and Venus ? 
A. It is their passage across the sun's disc. 

Q. What is the disc of the sun or a planet? 
A. It is the circular illuminated surface visible to us. 

Q. How do Mercury and Venus appear, when passing across the 
sun's disc ? 

A. They appear like black spots moving across the 

sun. 

Q. What proof have we that Mercury and Venus are not luminous 
bodies? 

A. When viewed with the telescope they appear 

horned like the moon. 

Q. On which side of the sun does a transit begin ? 

A. On the east side, and terminates on the west side. 

THE SPOTS ON THE SUN. 

Astronomers do not agree, in all respects, as to the cause of thespots on the sun From the facts 
already known, the following appears to be the most rational view of the subject. The body of the 
sun, which is opake, is surrounded by a- transparent atmosphere, in which float two strata.of lumi- 
nous clouds ; the lower stratum being more dense and opake, and less luminous than the upper; 
while the latter, by its brilliancy, furnishes the greater portion of the intense light of the sun. 
Above the upper stratum, the transparent atmosphere extends to a great height. The: agency by 
which the light and heat of the sun are generated, is not known. The only agent of which we 
know, that presents analogous phenomena, is electricity. The northern lights are supposed to 
exhibit, in a feeble manner, an action similar to the luminous strata of the sun. The polar regions 
of the sun are tranquil, and the equatorial comparatively so ; but the surface on each side of the 
equator, from 15 to 25 degrees therefrom, is in a state of constant and violent agitation It is in this 
disturbed region that the spots are seen ; no spot ever occurring farther than about 30 degrees from ■ 
the equator. The spots, besides revolving with the sun, are found to have a motion from the equa- 
tor towards the poles, and when they arrive at the comparatively calm region, they gradually dis- 
appear. Sometimes they close up with great rapidity, at others they appear to be suddenly broken 
into fragments and dispersed. Bright spots and streaks, called faculoe, apparently caused by waves 
in the luminous portion of the atmosphere, also appear on various parts of the disc, but are seen 
most distinctly near the margin. In the places where spots appear, faculae are usually seen on the. 
day previous to their breaking out. 

But what causes the agitation of. the sun's atmosphere, which Is so great as frequently to burst 
open the luminous strata ? Astronomers, at different times, have suggested various causes for-fche 
sun's spots, such as jets of gas issuing from the sun and decomposing the luminous clouds ; high 
mountains, extending through the luminous strata; volcanoes, sending forth ashes, smoke, &c.; 
to say nothing of exploded theories of an older date, such as ashes, scoriae, &c, on the surface of 
the melted, burning mass ; or bodies very near the sun, revolving round it. But if we are permit- 
ted to reason from what takes place on the earth, we would say, that a close analogy exists 
between the phenomena observed in our own atmosphere and in that of the sun- On the earth the 
heat of the torrid zone causes the air to expand and rise, causing currents in the lower part of the 
atmosphere towards the equator, and in the upper part of the atmosphere currents towards the 
poles. The turning of the earth on its axis causes the under currents to take a westerly direction, 
while the upper currents sweep in a curve, westerly first, then towards the poles, and finally east- 
ward. The principal disturbance of the atmosphere caused by the trade wind is in the vicinity of 
the tropics. Storms commencing in the torrid zone, are carried in the direction of the upper cur- 
rents of air, Forinstance, a storm started in the West Indies, by the heating of the air over one of 
its islands, thus causing an upward and circular movement of the air, usually sweeps to the west 
and north over Florida, or the Gulf of Mexico, and then northeast, over the United States. " Similar 
causes.acting upon the atmosphere of the sun, would exhibit phenomena similar to those which we 
see. This explanation supposes the atmosphere of the sun to be warmer at the equator than at the 
poles ; but as the sun does not, like the earth, receive its heat from any extraneous body, its differ- 
ence of temperature must be sought for in the escape of its heat. It could attain this condition 
either by a more free radiation of heat at -the* poles than' at the equator,-or by its absorptionas latent 
heat, in the evaporation from large bodies of water in the polar regions. As the sun turns on its 
axis, its equatorial diameter must be greater than its polar, and the stratum of atmosphere above 
the luminous clouds must be thicker over the equatorial region than over the polar. This must 
render the radiation less free at the equator than at the poles, and cause that part of the sun.to be of 
a higher temperature. An excess of beat-at the sun's equator, with its rotation on its axis, is suffi- 
cient to cause currents in its atmosphere similar .to our trade winds, and thus disturb its equatorial 
regions; and if the spots are caused by storms bursting open the luminous strata, their receding 
from the equator towards the pofes is undoubtedly the effect of the same physical causes that give 
a similar motion to storms upon the earth. 

Some have supposed the body of the sun to be protected by the lower opake portion of the inner 
stratum of clouds, from the intense heat of the luminous strata, and thus rendered inhabitable ; but 
several objections will at once arise to this theory. . First, the body of the sun being surrouriaed by 
dense and opake clouds, could not Bend off' its heat.into space by radiation, and therefore the heat 
received from the clouds would accumulate and cause'a high temperature. Second, the force of 
gravity- being about thirty times as great as that of the earth, a common sized man would weigh 
some two or three tons ; rendering it necessary to have an entirely different muscular organization. 
Third, it is improbable that living beings would be shut up within an impenetrable veil, *nd cut off 
from a knowledge of the planets, the stars, and the countless wonders existing in the boundless 
realms of- space. These and other considerations -render it probable that the sun is not inhabited. 









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ILLUSTRATED ASTRONOMY 



15 



LESSON XIV. 

ZODIAC. 

Question. What is the Zodiac? 

Answer. It is a circular belt in the heavens 16 degrees 
wide ; 8 degrees on each side of the ecliptic. 

Q. How is the zodiac divided ? 

A. It. is divided into 12 equal parts, called signs or 
constellations of the zodiac. 

Q. How is each sign divided ? 

A. Each sign is divided into 30 degrees; each degree 
into 60 minutes; each minute into 60 seconds, &c. 

Q. What great circle is in the middle of the zodiac? 

A. The ecliptic, or orbit of the earth. 

Q. What are the names of the constellations of the zodiac and the 
signs of the ecliptic ? 

A. Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, 
Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces. 

Q. Do the constellations of the zodiac and the signs of the ecliptic 
occupy the same places in the heavens ? 

A. They do not: the signs in the ecliptic have fallen 
back of the constellations about 31 degrees. 

Q. Did the constellations of the zodiac and signs of the ecliptic ever 
correspond ? 

A. They corresponded to each other about 22 centu- 
ries ago. 

Q. What is the cause of the falling back of the signs of the ecliptic 
among the constellations? 

A. It is caused by the retrograde motion of the equi- 
noxes. (Note.) 

Q. Upon what does the length of the seasons depend ? 
A. They depend upon the revolution of the earth 
from one equinox to the same, again. 

Q. Does the earth revolve around the sun in exactly the same time 
that it moves from one equinox to the same equinox again ? 

A. It moves from either equinox to the same again, 
seventeen minutes sooner, than around the sun. 



LESSON XV. 

Question. Does the sun appear to move in the heavens among the 
sta 's? 

Answer. It has an apparent motion in the ecliptic, east- 
ward around the heavens, during the year. 

Q. How is this appearance caused, as the sun is in the centre, and 
Joes not move ? 

A. It is caused by the earth's moving around the sun. 

Q. If the earth is in the sign Aries, where does the sun appear to be? 

A. It appears to be in the opposite sign, Libra. 

Q. A.s the earth moves around in the ecliptic, where does the sun 
appear to move ? 

A. It appears to move in the opposite part of the hea- 
vens, and in the^opposite direction from the motion of 
the earth. 

Q. Which sign does the sun enter, when the north pole leans exactly 
towards the sun ? 

A. Cancer. (21st June.) 



Q. Which sign does the earth enter at this time ? 
A. Capricornus. 

Q. Which signs does the sun enter, when the north pole leans side- 
ways to the sun ? 

A. Aries and Libra. 

Q. Which sign docs the sun enter, when the north pole leans exactly 
from the sun ? 

A. Capricornus. (22d December.) 
Q. Which are the equinoctial signs ? 
A. Aries, 21st of March — Libra, 23d of September. 

Q. Which are the solstitial signs ? 

A. Cancer, 21st of June — Capricornus, 22d of De- 
cember. 



LESSON XVI . 

Question. How are the signs of the ecliptic divided ? 
Answer. They are divided into four divisions, corres- 
ponding to the seasons. 

Q. Which are the spring signs? 

A. Aries, Taurus, Gemini. 

Q. Which are the summer signs ? 
A. Cancer, Leo, Virgo. 

Q. Which are the autumnal signs ? 

A. Libra, Scorpio, Sagittarius. 

Q. Which are the winter signs? 

A. Capricornus, Aquarius, Pisces. 

Q. In what time do the equinoxes fall back through the whole circle 
of the Zodiac ? 

A. 25,800 years. 

Q. What is this time called ? 

A. The Platonic, or great year. 

Q. How is this motion caused ? 

A. It is caused by a slow annual motion of the earth's 
axis. (Note.) 

Q. What is longitude in the heavens ? 

A. It is the distance from the first degree of the sign 
Aries, reckoned eastward on the ecliptic, the whole 
circumference of the heavens. 

Q. When the sun enters Aries, what is its longitude ? 

A. It has no longitude. 

Q. What is the longitude of the earth at that time ? 
A. 180 degrees. 

Q. When the sun enters Cancer, what is its longitude ? 

A. 90 degrees — the earth's longitude at the same 
time 270 degrees. 

Q. When the sun enters Libra, what is its longitude ?' 

A. 180 degrees — the earth's longitude degrees. 

Q. When the sun enters Capricornus, what is the longitude? 

A. 270 degrees — the earth's longitude at the same 
time 90 degrees. 

[Note.— This variation is caused by the pole of the earth varying a little every year. This mo- 
tion of the pole of the earth is similar to that sometimes shown by a top. as it spins around on the 
point — The stem of the top will have a circular motion, describing a cone with the apex or top 
down. This circular motion of the pole of the earth is very slow, varying only 50" every year, 
and requires '25.S6S years to complete a revolution — which is called the Platonic or great year. 
The pole of the earth is increasing its distance from the north star and in 1-2,900 years it will be about 
47° from it : and when the north star is on the meridian, it will be in the zenith of the northern 
part of the United States : but in -25.800 years the pole will have made a complete revolution -bo 
that it will point again to the north star.] 



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ILLUSTRATED ASTRONOMY 



17 



LESSON XVII. 
MERCURY. 

Question. Which planet is the smallest and nearest the sun? 

Answer. Mercury. 

Q. What is the diameter of Mercury? 

A. 3,200 miles. 

Q. What is its distance from the sun ? 
A. 37 millions of miles. 

Q. What is its magnitude, compared with the earth ? 
A. It is rr of the earth's magnitude. 

Q. What is the specific gravity of the planet Mercury? 

A. It is about 15 times the weight of water. (15.111.) 

Q. In what time does it revolve on its axis, or perform its daily revo- 
lution ? 

A. In about 24 hours. (24 hours 5 minutes.) 

Q. In what time does it revolve around the sun ? 

A. In about 88 days. (87d. 23h. 14m. 33s.) 
Q. How fast does it move in its orbit around the sun? 
A. It moves 112,000 miles an hour. 

Q. What is the light or heat at Mercury, compared with that of the 
earth ? 
A. It is about seven times as great. 

Q. What is elongation ? 

A. It is the apparent distance of any planet from (be 
sun. 

Q. What is the greatest elongation of Mercury? 

A. 30 degrees ; which may be either east or west of 
the sun. 

Q. Why is Mercury never seen in superior conjunction ? 

A. Because it is so much involved in the light of the 
sun. 

Q. Does Mercury experience any change of seasons ? 

A. It does not, because its axis is perpendicular to its 
orbit. This causes the sun to be continually vertical 
at the equator. 



LESSON XVIII. 
VENUS. 

Question. What planet is next to Mercury ? 

Answer. Venus. 

Q. What is the diameter of Venus ? 

A. 7,700 miles. 

: Q. What is its distance from the sun 
A. 68 millions of miles. 

Q. What is its magnitude compared with the earth? 

A. It is about T U o of the earth's magnitude. 

Q. What is the specific gravity of Venus ? 
A. It is 5 times the weight of water. (5.058.) 

Q. In what time does it revolve on its axis ? 
A. Iivabout 234 hours.- (23h. 21m.) 

Q. In what time does it revolve around the sun ? 

A. In 224 days. (224d. 16h, 41m. 27s.) 

Q. How fast does it move in it's orbit around the sun ? 
A. It moves 75,000 miles an hour. 

Q. What is the comparative light or heat at Venus ? 

A. It is about double that of the earth. 

Q. What is the greatest elongation of Venus ? 
A. About 47 degrees. 

Q. When is Venus a morning star? 

A. When it is west of the sun, and rises before it. 

Q. When is it an evening star ? 

A. When it is east of the sun, and sets after it. 



Q. How long is Venus a morning or an evening ttar, alternately 1 

A. About 290 days. 

Q. Why is Venus a morning or an evening star 66 days longer than 
the time of its revolution around the sun ? 

A. Because the earth is moving around the sun the 
same way. 

[See diagram. If we suppose Venus to be in conjunction, or between 
the earth and sun, as they move the same way, Venus will move 
half around the sun, or 180 degrees, while the earth moves only 110 
degrees. Venus will during this time be a morning star, and when 
Venus has completed its revolution around the sun, the earth will have 
passed through 220 degrees of its orbit, and Venus will still continue a 
morning star, although it has made a complete revolution around the 
sun. It will therefore have to make one complete revolution and 103 
degrees over, before it can be seen on the other side of (he sun ; it will 
then be an evening star for the same length of time.] 



LESSON XIX. 

Question. How much is the axis of Venus inclined to that of its orbit? 

Answer. 75 degrees. 

Q. When the north pole of Venus inclines directly towards the sun, 
how many degrees will the axis point above the sun ? 

A. Only 15 degrees. 
Q. How wide a torrid zone does this make ? 

A. 150 degrees— 75 degrees on each side of the 
equator. 

Q. The tropics are within how many degrees of the poles? 
A. Within 15 degrees. 

0. The polar circles are within how many degrees of the equator? 

A. 15 degrees. 

Q. What is the diameter of the polar circles ? 
A. 150 degrees. 

Q. Has Venus any variation of seasons ? 

A. She has two summers and two winters at the 
equator, and a summer and winter at each of the poles, 
during the year. 

Q. flow does Venus appear when viewed with a telescope ? 

A. She exhibits phases similar to those of the moon. 

Q. How are conjunctions divided ? 
A. Into inferior and superior. 

Q. When is a planet in inferior conjunction ? 
A. When it is between the earth and sun. 

Q. What planets have inferior conjunction ? 

A. Mercury and Venus ; also the moon. 

Q. When is a planet in superior conjunction ? 

A. When it is beyond the sun. 

Q. What planets have superior conjunction ? 
A. All, except the earth. 
Q. When is a planet in opposition to the sun? 

A. When it is on the opposite side of the earth. 

Q. What planets have opposition ? 

A. The superior planets. 

Q. What apparent motions have the planets ? 
A. Three; direct, stationary, and retrograde. 

Q. When does a planet's motion appear to be direct ? 
A. When it appears to move from west to east among 
the stars. 

Q. When is a planet's motion said to be stationary ? 

A. When it is moving directly towards or from the 
earth. 

Q. When is a planet's motion said to be retrograde ? 

A. When it appears to move backwards, or from east 
to west among the stars. 



ILLUSTRATED ASTRONOMY 



19 



LESSON XX. 
EARTH, DEFINITIONS, &c. 

Question. What i9 the shape of the earth? 



flat- 



Ansiver. It is round like a globe or ball, a little 
tened at the poles. 

Q. How do we know the earth to be round ? 

A. 1st. Navigators have sailed round it, by a con- 
tinued westerly or easterly course. — 2d. The top-mast 
of a ship coming in from the sea, always appears first. — 
3d. The earth's shadow upon the moon, in a lunar 
eclipse, is circular. 

Q. In what manner do the inhabitants stand upon the earth ? 

A. They stand with their feet directed towards the 
centre of the earth. (See Diagram.) 

Q. What do you understand by the terms upward and downward ? 

A. Upward is from the centre of the earth, downward 
is towards the centre of the earth. 

Q. What keeps the inhabitants, &c, upon the surface of the earth ? 
A. The attraction of the earth. 
Q. What is the axis of the earth? - 

A. It is the straight line round which it performs its 
daily revolution. 

Q. What are the poles of the earth ? 

A. They are the extremities of its axis. 

Q. What is the equator? 

A. It is a great circle, whose plane divides the earth 
into northern and southern hemispheres. 

Q. To what is the plane of the equator perpendicular? 

A. It is perpendicular to the earth's axis, and equi- 
distant from the poles. 

Q. What is the meridian of a place on the earth? 

A. It is a great circle passing through the place, and 
the poles of the earth. 

^. Into what does the plane of the meridian divide the earth? 

A. Into eastern and western hemispheres. 

Q. What is the latitude of a place on the earth ? 

A. It is its distance from the equator, north or south. 

Q. On what is it measured ? 

A. On a meridian ? 

Q. How far is latitude reckoned ? 

A. Ninety degrees ? 
Q. What places have 90 degrees of latitude? 

A. The poles. 

LESSON XXI. 

Q. Which is the first meridian? 

A. It is the meridian from which longitude is reck- 
oned. 

Q. Which meridian is generally used in this country as the first 
meridian ? 

A. The meridian of London. 

Q. What is the longitude of a place on the earth? 

A. It is its distance east or west of the first meridian. 

Q. What angle expresses the longitude of a place? 

A. The angle between the meridian of the place, and 
the first meridian. 

Q. Where is this angle formed? 

A. At the poles, where the meridians intersect each 
other. 

Q. On what circle is this angle measured ? 
A. On the equator. 



Q. How far is terrestrial longitude reckoned ? 

A. It is reckoned 180 degrees, or half round the earth. 

Q. What is the horizon ? 

A. It is a great circle which separates the visible 
heavens from the invisible. 

Q. How many horizons are there ? 

A. Two ; the visible and the rational. 

Q. What is the visible or sensible horizon ? 

A. It is that circle where the earth and sky appear 

to meet. 

Q. What is the rational horizon ? 

A. It is a great circle, parallel to the visible horizon, 
whose plane passes through the centre of the earth. 

(£. Into what does it divide the earth ? 

A. Into upper and lower hemispheres. 

Q. Is the rational horizon above or below the visible horizon ? . 

A. It is below the visible horizon. 



LESSON XXII. 

Q. Do all places on the earth have the same horizon ? 
A. They do not; if we change our place on the earth, 
the horizon changes. 

Q. What are the poles of the horizon? 
A. The zenith and nadir. 

Q. What is the zenith ? 

A. It is that point in the heavens directly oyer our 
heads. 

Q. Do all places have the same zenith ? 

A. They do not ; every place has a different zenith. 

Q. What is the nadir ? 

A. It is that point in the heavens which is opposite to 
the zenith, or directly under our feet. 

Q. Are the zenith and nadir fixed points in the heavens ? 

A. They are not ; they make a complete revolution 
in the heavens every 24 hours. 

Q. What is the altitude of a heavenly body? 

A. It is its height or distance from the horizon. 

Q. What is the altitude of the star at A? (See Diagram.) 

A. It has no altitude, being in the horizon. 

Q. What is the altitude of the star at B ? also at C ? (See Diagram.) 
Q. What is the polar distance of a heavenly body? 

A. It is its distance from the pole. 

Q. What is the polar distance of the star at D ? also at E. and F ? 
(See Diagram.) 

Q. Who are the antipodes? 

A. Those who live on directly opposite sides of the 
earth. 

Q. Who are the antceci ? 

A. Those who live in equal latitude, on directly oppo- 
site sides of the equator. 

Q. Who are the periceci ■?■ 

A. Those who live in equal latitude on opposite sides 
of the pole. 

Q. What peculiarity of circumstances have the antipodes? 

A. They have opposite latitude, seasons, longitude, 
and day and night. 

Q. What have the antceci ? 

A. They have opposite latitude and seasons, but the 
same longitude, and day and night. 

Q. What have the periceci ? 

A. They have the same latitude and seasons, but 
opposite longitude, and day and night. 



ILLUSTRATED ASTRONOMY, 



21 



LESSON XXIII. 
EARTH AND SEASONS. 

Question. What is the shape of the earth ? 

Answer. It is round like a globe or ball, a Httle flat- 
tened at the poles 

Q. What is its position in the solar system ? 
A. It is the third planet from the sun. 
Q. What is the mean diameter of the earth? 
^i. 7,912 miles. [Equatorial diameter 7,926 miles; 
polar diameter 7,899 miles.) 

Q. How much greater is the equatorial than the polar diameter ? 

A. About 27 miles. 

Q. What causes the equatorial diameter to be greater than the polar ? 

A. It is caused by the revolution of the earth on its 
axis. 

[As the greater portion of the surface of the earth is covered with 
water ; and as the earth revolves on its axis, the water recedes from 
the poles towards the equator, until its tendency to run back towards 
the poles, just balances the effects of the centrifugal force. This 
causes the equatorial diameter to be greater than the polar. If the 
earth should stop revolving on its axis, the water at the equator would 
settle away towards the poles, until the earth had assumed the form of 
a globe as near as possible. Thus large portions of land in the torrid 
zone, which are now covered by the ocean, would be left dry, and new 
continents and islands would be formed.] 

Q. What is the mean distance of the earth from the sun ? 

A. About 95,000,000 of miles. 

[The mean distance of a planet, is the distance it would always bo 
from the sun, if its orbit should be reduced to a true circle.] 
Q. What is the specific gravity of the earth? 

J.. It is 5h times the weight of water. (5.48.) 

Q. In what time does the earth revolve on its axis, or perform its 
diurnal revolution ? 

A. In 24 hours. (In 23 hours 56 minutes ; as seen 
from the stars.) 

Q. Which way does it revolve ? 

A. From west to east. 

Q. What causes day and night ? 

A. The light of the sun causes day, and the shade 
of the earth causes night. 

Q. How great a portion of the earth is continually in the light of the 
sun ? 

A. One half; the other half being in the shade of the 
earth. 

Q. What does the revolution of the earth upon its axis, cause ? 

A. The succession of day and night. 



LESSON XXIV. 

Question. As the earth turns upon its axis, what effect is produced ? 

Answer. The sun is continually rising to places in the 

west, and continually setting to places in the east. 

0. In what time does the earth revolve around the sun, or perform 
its annual revolution ? 

A. In 365 days 6 hours. 

Q. How fast does it move in its orbit around the sun ? 

A. 68,000 miles an hour. 

Q. How are the changes of the seasons caused ? 

A. They are caused by the earth's axis being inclined 
to that of its orbit, and its revolution around the sun. 



Q. How many degrees is the earth's axis inclined towards its 
orbit ? 

A. Twenty-three degrees and a half. (23° 28'.) 

Q. Is the direction of the earth's axis changed during the year? 

A. Its change is so slight that it may be considered 
as pointing to the same place in the heavens. 

Q. When does the north pole lean directly towards the sun ? 

A. On the 21st of June, called the summer solstice. 
(See Diagram.) 

Q. How many degrees does it lean towards the sun ? 

A. 23^ degrees ; and the sun is vertical 23i degrees 
north of the equator. 

Q. What seasons does this produce ? 

A. Summer in the northern hemisphere, and winter 
in the southern. 

Q. When does the north pole lean directly from the sun ? 

A. On the 22d of December, called the winter sol- 
stice. (See Diagram.) 

Q. When the north pole leans from the sun, what are the sea- 
sons ? 

A. Winter in the northern hemisphere, and summer 
in the southern. 



LESSON XXV. 

Question. At what points of the ecliptic is the earth at the time of 
the solstices ? 

A. At the solstitial points. 

Q. Through how much of its orbit does the earth pass, in moving 
from one solstitial point to the other? 

A. One half of its orbit, or from one side of the sun to 
the other. 

Q. What are those two points called half way between the solstitial 
points ? 

A. The equinoctial points. (See Diagram.) 

Q. Why are they so called ? 

A. Because, when the earth is in these points, the 
sun is vertical at the equator, and the days and nights 
are every where equal. 

Q. When is the sun at the vernal equinox ? 

A. On the 21st of March. 

Q. When is it at the autumnal equinox ? 

A. On the 23d of September. 

Q. Which way does the pole lean when the earth is at the eqinoc- 
tial points ? 

A. It leans sideways to the sun, the sun being verti- 
cal at the equator. 

Q. When the north pole leans towards the sun, why is summer pro- 
duced in the northern hemisphere ? 

A. Because the rays of the sun strike it so directly as 
to cause many rays to fall on a given surface. 

Q. When the north pole leans from the sun, why is winter produced 
in the northern hemisphere ? 

A. Because the rays of the sun strike it so obliquely, 

that they spread over a greater surface. 

Q. At what points do the ecliptic and equinoctial intersect each 
other ? 

A. At the equinoctial points. (See Diagram.) 

Q. How far are the solstitial points from the equinoctial points ? 
A. Ninety degrees. 



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ILLUSTRATED ASTRONOMY. 



23 






AEROLITES, METEORS, &c. 
Question. What are meteors? 

Answer. They are luminous bodies seen in the night 
shooting through the heavens. 

Q. What are they usually called ? 

Shooting stars, and sometimes fire-balls. 

What is an aerolite ? 



A. 

Q. 

A. 

Q. 



It is a stone falling from the air. 



Have stories ever been known to fall from the air? 

A. They have, and in great numbers. (See Table.) 

Q. How did Laplace, Olbers, and other astronomers account for 
the falling of these stones? 

A. They believed that they were ejected from vol- 
canos in the moon, beyond the moon's attraction, and 
therefore attracted to the earth. 

Q. How did they account for the meteors 1 

A. They believed them to be gaseous matter col- 
lected in the upper regions, and ignited by some un- 
known cause. 

Q. What is the present theory in regard to aerolites and meteors? 

A. Astronomers believe that they have the same 
origin. 

Q. Do all meteors produce stones which fall to the earth ? 

A. They do not; very few of them are of suffi- 
cient density to reacli the earth before they are 
consumed. 

Q. Do these meteors originate in our atmosphere ? 

A. The most of them have their origin far beyond 
our atmosphere. 

Q. What is the present theory of meteors ? 

A. Astronomers maintain that the planetary regions 
contain detached portions of chaotic and uncon- 
densed matter, and that the earth in its orbit fre- 
quently meets with such masses. 

Q. What effect would be produced by such contact? 

A. The matter in its passage through the atmos- 
phere would suddenly be ignited and the gaseous 
portion consumed, and the mineral portion, if any, 
would be condensed and precipitated to the earth in 
the form of a stone. 

Q. What is a peculiar characteristic of meteoric stones? 

A. They are composed of the same materials and 
nearly in the same proportions, and are unlike any 
combination of minerals found on the earth. 

Q. What does this fact prove ? 

A. It conclusively proves that they have a common 



origin. 



Q. When was the greatest meteoric display ever known ? 
Note 2.) 



(See 



A. On the night of the 12th and 13th of November, 
1833. 

Q. What was the altitude of the meteors on this occasion ? 

A. Professor Olmstead says they were not less than 
2238 miles above the earth. 









Substance. 


Place. 


Period. 


Shower of stones 


At [tome 


Under Tullus Hostilms. 


Shower of stones 


At Rome 


Consuls C. Martius and Tor- 

quatus. 
Year before the defeat of 


Shower of iron 


In Lucania 


Crassus. 


Shower of mercury 


In Italy 




Large stone 


Near the river Negos, Thrace 


Second year of the 78th Olym- 
piad. 
Year before J. C. 452. 


Three large stones 


In Thrace 


Shower of fire 


At Quesnoy 


January 4, 1717. 


Stone of 72 lbs. 


Near Larissa, Macedonia 


January, 1706. 








Ins , another of 60 lbs. J 


Near Padua. Italy 1 


In 1510. 


Another of 59 lbs. 


On Mount Vasier, Province 


November 27, 1627. 


Shower of Sand for 15 hours 


In the Atlantic 


April 6, 1719. 


Shower of sulphur 


Sodom and Gomorra 




Sulphurous rain 


In the Duchy of Mansfield 


In 1658. 


The same 


Copenhagen 


In 1646. 


Shower of sulphur 


Brunswick 


October, 1721. 


Shower of unknown matter 


Ireland 


In 1695. 


Two large stones, weighing / 
20 lbs. J 


Liponas, in Bresse 


September, 1753. 


A stony mass 


^Niort, Normandy 


In 1760. 


A stone of 7 1-2 lbs. 


At Luce, in Le Maine 


September 13, 1768. 


A stone 


At Aire, in Artois 


In 1768. 


A stone 


In Le Cotenlin 


In 1768. 


Extensive shower of stones 


Environs of Agen 


July 24, 1790. 


About 12 stones 


Sienna, Tuscan)' 


July. 1794 


A large stone of 56 lbs. 


Wold Cottage, Yorkshire 


December 13, 1795. 


A stone of about 20 lbs. 


Sale, Department of the Rhone 


March 17, 1768. 


A stone of 10 lbs. 


In Portugal 


Februarv 19, 1796. 


Shower of stones 


Benares, East Indies 


December 19, 1798. 


Shower of stones 


At Plann, near Tabor, Bohemia 


July 3, 1753. 


Mass of iron, 70 cubic feet 


America 


April 5. 1S0O. 


.Mass of iron, 14 quintals 


Abakauk, Siberia 


Very old. 


Shower of stones 


Barboutan, near Roquefort 


July, 1789. 


Large stone of 260 lbs. 


Ensisheim, Upper Rhine 


November 7, 1492. 


Two stones. 200 and 300 lbs. 


Near Verona 


In 1762. 


A stone of 20 lbs. 


Sules, near Ville Franche 


March 12, 1798 


Several stones from 10 to 17 I 
lbs S 


Near L'Aigle, Normandy 


April 26, 1803. 



NOTE. 

One of the instances in the table is of sufficient interest to deserve a notice. 

A singular relation respecting the stone of Ensisheim on the Khine, (at which 
philosophy once smiled incredulously, regarding it as one of the romances of the 
middle ages.) may now be admitted to sober attention as a piece of authentic history. 
A homely narrative of its fall was drawn up at the time by order of the emperor Max- 
imilian, and deposited with the stone in the church. It may thus be rendered : — " In 
the year of the Lord 1-192, on Wednesday, which was Martinmas eve, the 7th of 
November, a singular miracle occurred ; for, between eleven o'clock and noon, there 
was a loud clap of thunder, and a prolonged confused noise, which was heard at a 
great distance ; and a stone fell from the air, in the jurisdiction of Ensisheim, which 
weighed two hundred and sixtv pounds, and the confused noise was, besides, much 
louder than here. Then a child saw it strike on a field in the upper jurisdiction, 
towards the Khine and Inn, near the district of Giseano, which was sown wjth wheat, 
and it did it no harm, except that it made a hole there ; and then they conveyed it from 
that spot; and many pieces were broken from it, which the landvogt forbade. They, 
therefore, caused it to be placed in the church, with the intention of suspending it as a 
miracle : and there came here many people to see this stone So there were remarka- 
able conversations about this stone: but the learned said that they knew not what it 
was ; for it was beyond the ordinary course of nature that such a large stone should 
smite the earth from the height of the air ; but that it was really a miracle of God : for, 
before that time, never anything was heard like it, nor seen, nor described. When 
they found that stone, it had entered into the earth to the depth of a man's stature, 
which every body explained to be the will of God that it should be found ; and the 
noise of it was heard at Lucerne, at Vitting, and in many other places, so loud that it 
was believed that houses had been overturned : and as the King Maximilian was here 
the Monday after St. Catharine's day of the same year, his royal Excellency ordered 
the stone which had fallen to Be brought to the Castle, and, after having conversed a 
Jong time about it with the noblemen, he said that the people of Ensisheim should take 
it, and order it to be hung up in the church, and not to allow any body to take anything 
from it. His Excellency, however, took two pieces of it ; of which he kept one, and 
sent the other to the Duke ;-igismund of Austria : and they spoke a great deal about 
this stone, which they suspended in the choir, where it still is ; and a great many peo- 
ple came to see it." Contemporary writers confirm the substance of this narration, 
and the evidence of the fact exists ; this aerolite is precisely identical in its chemical 
composition with that of other meteoric stones. It remained for three centuries sus- 
pended in the church, was carried off to Colmar during the French revolution ; but 
has since been restored to its former site, and Ensisheim rejoices in the possession of 
the relic. 

NOTE 2. 

We now come to by far the most splendid display oil record ; and as it was the third 
in successive years, and on the same day of the month, it seemed to invest the 
meteoric showers with a periodical character ; and hence originated the title of 
November meteors. An incessent play of dazzlingly brilliant meteors was kept up in 
the heavens for several hours- Some of these were of considerable magnitude and 
peculiar form. One of large size remained for some time almost stationary in the zenith, 
over the Falls of Niagara, emitting streams of light. The wild dash of the waters, as 
contrasted with the fiery uproar ahove them, formed a scene of unequalled sublimity. 
In many districts, the mass of the population were terror-struck, and the more enlight- 
ened were awed at contemplating so vivid a picture of the Apocalyptic image — that of 
the stars of heaven falling to the earth, even as a fig-tree casting her untimely figs, when 
she is shaken of a mighty wind. A planter of South Carolina thus describes the effect 
of the scene upon the ignorant blacks: — " I was suddenly awakened by the most dis- 
tressing cries that ever fell on my ears. . Shrieks of horror and cries for mercy I could 
hear from most of the negroes of three plantations, amounting in all to about six or 
eight hundred. While earnestly listening for the cause, I heard a faint voice near the 
door calling my name. I arose, and taking my sword, stood at the door. At this 
moment. I heard the same voice still beseeching me to rise, and saying ' O my God, 
the world is on fire.' I then opened the door, and it is difficult to say which excited 
me most — the awfulness of the scene, or the distressed cries of the negroes. Upwards 
of one hundred lay prostrate on the ground — some speechless, and some with the bit- 
terest cries, but wiih their hands raised, imploring God to save the world and them. 
The scene was truly awful ; for never did rain fad much thicker than the meteors fell 
towards the earth; east, west, north and south, it was the same." 



J 



ILLUSTRATED ASTRONOMY 



25 



LESSON XXVI. 

MARS. 

Question. What is Mars ? 

Answer. Mars is the fourth planet from the sun. 

Q. What can you say of its size ? 

A. IMs the smallest except Mercury and the asteroids. 

Q. What is- its diameter ? • 

A. 4,189 miles. 

Q. What is its distance from the sun ? 

A. 142 millions of miles. • ' 

Q. What is its magnitude ?' 

A. It is about one seventh of the size of the earth. 

Q. What is the specific gravity of Mars? 

A. It is about five times the weight of water. (5.19.) 

Q. In what time does it revolve on its axis ? 

A. In about 24i hours. (24h. 39m. 22s.) 

Q. In what time doestit revolve around the sun ? 

A. In one year, 321 days. 

Q. How fast does it move in its orbit? 

A. 55,000 miles an hour. 

Q. How man.v degrees does the axis of Mars lean towards its orbit? 

A. About 30 degrees, (30° 18'.) (See Diagram.) 

Q. Does Mars have any change of seasons? 

A.. The seasons are similar to those of the earth, but 
nearly twice as long. 

JQ. Why are they longer ? 

A. Because Mars is nearly two of our years in revolv- 
ing around the sun. 

Q. What is the appearance of Mars when seen with the naked eye? 

A. It appears of a red, fiery color. 



LESSON XXVII. 

Q. How does Mors appear when viewed with a telescope ? 

A. Outlines of apparent continents and seas, are dis- 
tinctly seen. 

Q. What appearance have the continents ? 

A. They have a ruddy color, arising probably from 
the nature of the soil. 

Q. Of what color are the seas ? 

A. They appear of a greenish color, caused no doubt 
by contrast with the red color of the continents. 

Q. Does Mars present different phases? 

A. It sometimes appears gibbous. 
Q. When does- a planet appear gibbous ? 

A. When we can see more than half, but not the 
whole, of the illuminated surface. 

Q. Does Mars ever appear horned like the moon ? 

A. It does not, because it does not pass between us 
and the sun. 

Q. What other appearances does Mars exhibit when viewed with a 
telescope ? 

A. Bright spots are seen alternately at the poles. 

Q. When do these spots appear? 

A. When it is winter, or continual night at the poles. 

Q. W : hat is supposed to be the cause of these spots? 

A. Snow and ice, which has accumulated at the poles 
during winter. 



Q. Do these spots continue through the year ? 

A. They entirely disappear as the summer advances 
upon the poles. 

Q. What amount of light and heat has Mars ? 

A. It has about half as much as the earth. 

ASTEROIDS. 

Question. What are the asteroids ? 

Answer. They are small bodies between the orbits 
of Mars and Jupiter. 

Q. How many are there ? 

A. Twenty three is the number known at present. 

Q. What is their magnitude ? 

A. They are very small with the exception of Pallas. 

Q. What have some astronomers supposed in regard to them ? 

A. That they were once united in one planet; but 
blown to pieces by some internal explosion. 

Q. What facts do they advance to prove this theory ? 

A. They are rough with sharp angular points, 

NOTE. 

Astronomers in comparing the distances of the planets, found that there was a 
great distance between Mars and Jupiter which did not coincide with the -unifor- 
mity exhibited by the other planets. This led them to suspect that there was an 
undiscovered planet- circulating in that region, and Baron de Za'ch went so far as 
to calculate in 1784—5, the orbit of this ideal planet. So confident were astrono- 
mers of the existence of a planet, that in 1800, six astronomers, of whom Baron 
de Zach was one, assembled at Lilienthal, and formed an association of twenty- 
four observers, the principal object of which was to use their own language " to 
force this planet from the regions of analogy into the realms of sense ; " but before 
they had got fully organized, Piazza discovered Ceres ; after another year Olbers 
discovered Pallas, and Juno, and Vesta were brought in at intervals of a few years. 
The search continued fruitless for ten years, it was fairly concluded that this region 
was exhausted. In consequence of the discovery of four small planets instead 
of one large planet, the new and somewhat novel idea was advanced by Dr. Olbers, 
that these bodies were originally united in one planet; but by some internal ex- 
plosion had been blown in pieces. 

This theory has been fully discussed by astronomers from that time to the pres- 
ent day. Several support the theory of Olbers, while others discard it entirely 
as untenable. In 1843, astronomers turned their telescopes again to this field for 
exploration, and they have succeeded in discovering nineteen new asteroids which 
makes the whole number twenty-three. The first four, Ceres, Pallas, Juno and 
Vesta are from the sixth to the eighth magnitude ; while the nineteen new ones 
are less than the ninth in magnitude; all of these bodies are very small and are 
rough with sharp angular points ; these facts would seem to indicate that they had 
formerly been united in one body. 

The following is a list of the names, date of discovery, and by whom discovered. 



Name and Number. 



1. 
2. 
3. 

4. 

5. 

6. 

7. 

8. 

9. 
10. 
11. 
12. 
13. 
14. 
1-5. 
16. 
17. 
18. 
19 
20. 
21 
22 '. 
23 



Ceres 

Pallas .. 

Juno 

Vesta. 

Astrea 

Hebe 

Iris 

Flora 

Metis 

Hvsceia 

Parthenope . 
Victoria 

F.geria 

Irene 

Runomia. . . . 

Psyche 

Thetis 

Meloomene. 
Fortuna . . . . 
Mnssilia. . . . 

Lotetia 

Calliope.-. . . 
Thalia. 



Date of Discovery. 



1800, 
1802, 
1S04. 
1807, 
1845, 
1847, 
1847, 
1847, 
1848, 
1849, 
1850, 
1850, 
1850, 
1S51, 
1851. 
1532, 
1852, 
1352. 
1852. 
1 8- r rt, 
1852. 
1852, 
1852, 



Jan. 1. 
Mar. 28. 
Sept. 1. 
Mar. 29. 
Dec. 8. 
July 1. 
A us;. 13. 
Oct 18. 
April 26. 
April 12. 
May 11. 
Sep. 13 
Nov. 2. 
Mav 19. 
Julv 29. 
Mar 17 
April 17. 
June 24 
Aug. 22 
Sept 19 
Nov. 15.. 
N..v. 16. 
Dec. 15. 



Name of Discoverer. 



Piazza, of Sicily. 

Olbers, of Bremen. 

Harding. 

Olbers. 

Hencke, of Germany. 

Hencke. 

Hind, of London. 

Hind. 

Graham, of Ireland. 

De Gasparis, of Naples. 

De Gasparis. 

Hind. 

De Gasparis. 

Hind 

De Gasparis. 

De Gasparis 

I.uther, of Germany. 

Hind. 

Hind 

De Gasparis. 

Goldschmidt, of Germany 

Hind 

Hind. 



ILLUSTRATED ASTRONOMY. 



27 



LESSON XXVIII. 

JUPITER. 

Question. What is Jupiter ? 

Answer. Jupiter is the largest planet in the solar 
system. • 

Q. How man}' times larger is Jupiter than the earth? 

A. It is 1,280 times greater. 

Q. What is the specific gravity of Jupiter ? 

A. It is about H times the weight of water. (1.30.) 

Q. How far is Jupiter from the sun ? 

A. 485 millions of miles. 

Q. What is its diameter* 

A. 87,000 miles. 

Q. Which diameter is the greater, the polar or equatorial ? 

A. The equatorial diameter is 6,000 miles greater 
than the polar. 

Q. What causes the equatorial diameter, so much to exceed the polar ? 

A. The quick rotation of the planet upon its axis. 

Q. In what time does it revolve upon its axis ? 

A. In about 10 hours. (9h. 55m. 50s.) 

Q. In what time does it revolve around the sun ? 

A. In eleven years, 314 days. 

Q. How fast does it move in its orbit around the .sun ? 

A. 30,000 miles an hour. 

Q. How many moons has Jupiter ? 

A. Four. 

Q. What is their magnitude ? 

A. They are about the size of our Moon. 

Q. Who first discovered them ? 

A. Galileo, the inventor of the telescope in 1610. 

Q. How are the orbits of these Moons situated ? 

A. They are directly over his equator. 

Q. Do these moons frequently eclipse the Sun ? 

A. They do at each revolution around the Sun. 

Q, What great discovery was made by observing these eclipses ? 

A. The velocity of Light. (Note.) 

Q. Has Jupiter any change- of seasons ? 

A. It has no change of seasons. 

Q. Why do its seasons not change ? 

A. Because its axis is nearly perpendicular to the 
plane of its orbit, which causes the sun to be always 
vertical at the equator. (See Diagram.) 

' Q. How does Jupiter appear, when viewed with a telescope ? 

A. Light and dark belts appear to surround it. (See 
Fig. 1 and 2.) 

Q. What are. the light belts ? 

A. They are supposed to be clouds, which are thrown 
into parallel lines by the quick rotation of the planet 
upon its axis. 

Q. What are the dark belts ? 

A. They are probably the body of the planet, seen 
between the clouds. 

Q. Do these belts always appear the same ? 

A. They change frequently, and sometimes the 
clouds break to pieces. (See Fig. 3.) 

Q. What is the velocity of its equatorial, parts, in turning on its axis ? 

A. 25,000 miles an hour. 
. Q. What amount of, light and heat has Jupiter ? 

A. It has 27 times less than the. earth. 



SATURN'S RINGS. 

(From the American Jllmanac and Repository of useful Knowledge, 1S52). 

"Within a few months the inquiry has been started with fresh interest, By how many rings is 
Saturn surrounded, and in what way are these rings sustained 7 Short saw two or three divisions 
outside of the centre of breadth. Herschel the first, in 1780. saw a new division near the inner 
edge. As this appearance was temporary, he thought that observation would not justify the sup- 
position of multiple rings Lines of demarcation were seen on both rings in 1313 and 1814. Que- 
telet saw the outer ring divided m 18-23 In 1825 and 1826 three divisions were seen on the outer 
ring by Kater. In 1837 Encke noticed that the outer ring was divided, and that there were se- 
veral marks near the inner edge of the inner ring. De Vico has given an account of several divi- 
sions seen by him on both rings. In 1838 several divisions were seen at Rome, which are described 
by Decuppis. In 1843. Lassell and Dawes saw a division of the outer ring. Smyth gives an ac- 
count of the last case, and adds : " After such unquestionable evidence, there can be no reason- 
able doubt of the outer ring's being multiple " On the 1 1th of November, 1350. G. P. Bond saw 
what he thought at the time a second division of the ring, near the inner edge of the inner ring. 
On the 15th, his father thought the new ring was wholly disconnected with the old, though the 
edge next to the planet was betteY defined than the outer edge. Micrometric observations gave 
for the inner diameter of the inner division 25" 3, whereas, according to Encke, the inner diameter 
of the old inner ring should be at that time 29"8. From this it was inferred that the large re- 
fractor at Cambridge had revealed an entirely unknown and darker ring of Saturn, which was not 
to be confounded with the division of the old inner ring which had frequently been noticed. The 
outer edge of the new ring is l".d within the inner edge of any ring hitherto visible. This con- 
clusion was confirmed by observations continued for several weeks. Similar appearances were 
noticed on the 25th and 26th of November, by Mr. Dawes, and afterwards by Lassell of Liverpool, 
and Schmidt of Bonn. 

On the 15th of April, 1S51, G P. Bond communicated to the American Academy of«^rts and 
Sciences at Boston, a memoir on the rings of Saturn. After rehearsing the facts already detailed 
in regard to extraordinary divisions of the rings, he draws attention to the circumstance that other 
observers, as Struve, Bessel, J, F. W. Herschel. and, we may add, Smyth, have seen only the usual 
division, even with the best instruments, and under the most favorable circumstances. More- 
over, the divisions on both rings are not always seen simultaneously ; and the Cambridge teles- 
cope which has brought to view a ring always before invisible, does not indicate any of the un- 
usual divisions in the two old rings. It seems, a justifiable conclusion from all the facts, that the 
multiplicity of rings occasionally seen, and the failure to discern more than two at other times, 
are not referrable to the difference of instruments, to the greater or less purity of the air, or to, 
the unequal skill of observers, but to a material fluctuation in the ring itself. 

In a lecture publicly delivered in Reading, Pennsylvania, on the 3d of January, 1851, Mr. 
Khkwood made the following remarks : — "This gives rise to the interesting question whether the 
rings of Saturn may not be the most recent cosmicat formation within the limits of the solar sys- 
tem, and whether it may not, in the course of future ages, collect about a nucleus and constitute a 
satellite The evidence of its solidity is not, I think, by any means conclusive. On the other 
hand, observations made within the last few years give'a degree of plausibility to the presumption 
that it may be in a state of fluidity. I refer to the occasional appearance of dark lines, chiefly on 
the outer* rings, which have been supposed to indicate a subdivision mto several concentric an- 
nuli. They do not. however, appear to be permanent ; at least they are subject to some change, 
as they are not always visible even when circumstances would seem most favorable. 

Such are the considerations which led Mr. Bond to reject the idea of solid rings, and to sup- 
pose these appendages of Saturn to be fluid or semi-fluid. If this is the material, it is unnecessary 
to suppose that the inner and outer surfaces move round in the same time. The velocity at every 
point may be such, that the centrifugal and other forces balance each other. " And even should 
an accumulation of disturbances, of which the absence of inequalities lessens the probability, _ 
bring the rings together, the velocities at the point of contact will be very nearly equal, and the 
two»will coalesce without disastrous consequences." " If, in its normal condition, the ring has but 
one division, as is commonly seen, under peculiar circumstances it might be anticipated'that the 
preservation of their equilibrium would require a separation in some regions of either the inner 
or outer ring ; this would explain the fact of occasional subdivisions being seen. There being 
visible but for a short time, and then disappearing to the most powerful- telescopes, is accounted 
for by the removal of the sources of disturbance, when the parts thrown Oft' would reunite " 

" Finally, a fluid ring, symmetrical in its dimensions, is not of necessity in a state of unstable 
equilibrium, with reference either to Saturn or the other rings." . " 

At the meeting at Cincinnati of the American Association for the Advancement of Science, 
Professor B Peirce, read a memoir on the constitution of Saturn's ring, containing the same, 
general views which he submitted to the American Academy of Arts and Sciences at Boston, on 
the 15th of April, 1851, Mr. Peirce arrives at the same results by analysis as those whjch Mr. 
Bond had derived from observations, illustrated and combined by his own ingenious computations, ' 
Mr Peirce differs in opinion from Laplace, in regard to the efficacy of an irregular figure in sus- 
taining Saturn's ring. He considers this statement of Laplace, which his successors have blindly 
adopted, as a careless suggestion, and not the rinened fruit of his usual rigid examination. " I 
maintain," he says, " unconditionally, that there is no conceivable form of irregularity, consistent 
with an actual ring, which would serve to retain if permanently about the primary, if it ive.re solid." 

The stability of the ring does not depend on the attraction exerted on it by the planet. 
In the circulation of the fluid annulus around Saturn, the velocity is least at the greatest dis- 
tance. Hence the matter accumulates at the most remote point of the ring, and to such an extent 
that the quantity of matter balances the distance, and the attraction exerted by the ring and the 
planet on-each other is the same in every direction. The ring is held together by the attraction 
of the primary ; but it is not sustained as a whole by the primary. It is sustained by the satellites. 
The satellites disturb it, and sustain it by a delicate equipoise of disturbances. Something like 
this restorative action had been hinted at by Sir J. F. W. Herschel. But the remedial power is insuf- 
ficient to sustain a solid ring. It follows that no planet can have a ring unless richly provided 
with menials to hold it. Saturn alone of all the planets seems competent to preserve a ring when 
once bestowed. 

Mr. Peirce concludes his memoir with the following weighty paragraph : "Were the ring, 
however, supposed to be a large gaseous mass of a circular figure, the condensation which would 
occur at the point of aphelion might easity lead to chemical action. Precipitation might ensue, 
and the necessary consequence would seem to he a continually accelerated accumulation at this 
point, which would terminate in the formation of a planet. Under this modification, the nebular 
hypothesis may possibly be free from some of' the objections with which it has been justly as- 
sailed. But in approaching the forbidden limits of humarTknowledge, it is becoming to tread with 
caution and circumspection. Man's speculations should be subdued from all rashness and extrav 
agance. in the immediate presence of the Creator. 

[The rings of Saturn hare been considered by the most celebrated astronomers, Laplace, Struve. 
Bessel, Sir William Herschel, J. F. "W. Herschel, Smyth and others, as being solid bodies surround- 
ing the planet and of the same materials and density ; hut Mr. G. P. Bond of Cambridge, and Pro- 
fessor Pierce, have advanced a new theory in regard to these rings, that they are a fluid or semi- 
Liquid matter. In regard to this novel Theory it is not considered by astronomers as fully estab- 
lished. We have not adopted this new theory in this work, preferring to wait for a further de- 
monstration of it. We are however inclined to believe that the various phenomena are more 
easily explained upon this hypothesis. — Author. 



NOTE. 

In 1675 it was observed by Roemer a Danish Astronomer, that when the earth Was nearest to 
Jupiter the eclipses of his sattellites took place S minutes 13 seconds sooner than the time specified 
in the astronomical tables ; but when the earth Was farthest from Jupiter, the eclipses took place 
8 minutes 13 seconds too late, the difference being 16m. 26s. From this it appears that it takes light 
16m. 26s. to pass across the earth's orbit which is 190 millons of miles in diameter— 190 millions of 
miles divided by 986 the number of seconds in 16m. 26s. gives 192,697 miles as the velocity of light 
per second. 



ILLUSTRATED ASTRONOMY 



29 



Q. 
A. 

Q. 



q. 
A. 

Q. 



LESSON XXIX. 
SATURN. 

Question. What is Saturn ? 

Answer. It is the largest planet except Jupiter. 

Q. What is its magnitude compared with the earth 1 
A. It is about 1,000 times larger. 

Q. What is its specific gravity ? 

A. It is about one half the weight of water. (0.56.) 
Q. What is the diameter of Saturn ? 

A. 79,000 miles. 

Q. What is its distance from the sun ? 
A. 890 millions of miles. 

In what time does it revolve on its axis ? 

In about 10* hours. (lOh. 29m. 16s.) 

In what time does it revolve around the sun ? 

A. In 29 years and a half. (29y. 167d.) 

Q. How fast does it move in its orbit around the sun ? 

A. 22,000 miles an hour. 

Q. Is there any change of seasons at Saturn? 

A. There is, but it is very slow, as it takes nearly 
thirty of our years, to complete a year at Saturn. 
Q. How much does the axis of Saturn lean towards its orbit? 
A. About 30 degrees. (28° 40'.) (See Diagram.) 
How long is it day and night alternately at the poles ? 
About 15 of our years. (See Diagram.) 

What has Saturn which surrounds it? 

A. Two large rings of solid matter like the planet. 
(See Diagram.) 

Q. What is their position around the planet ? 
A. They are directly over the equator. 

LESSON XXX. 

Q. Do these rings revolve with the planet ! 
A. They do, and in nearly the same time as the 
planet. 

Q. Are these rings connected with the planet or separate ? 
A. They are separate from the planet and from each 
other. 

Q. What is the distance from the planet to the inner ring ? 

A. 19,000 miles. 

Q. How wide is the inner ring ? 

A. 17,000 miles. 

Q. How wide is the space between the rings ? 
A. About 1,800 miles. 

Q. What is the width of the outer ring ? 

A. 10,000 miles. 

Q. How thick are these rings ? 

A. About 100 miles. (Some say 1,000 miles.) 

Q. Are these rings uniform ? 

A. They are rough and uneven. 

Q. How many satellites or moons has Saturn ? 
A. Eight. 

Q. What is the position of their orbits ? 

A. Their orbits, excepting one, are directly over the 
rings. (See Diagram.) 



Q. Does the sun always shine on the same side of the rings? 

A. It shines upon each side alternately for fifteen 

years. (See Diagram.) 

Q. What amount of light and heat has Saturn ? 
A. It has 90 times less than the earth. 

Q. What appearance has the disc of Saturn ! 

A. It has dark belts similar to those of Jupiter. 



Saturn. 

According to heathen mythology, Saturn was the deity who pre- 
sided over time. He is sometimes represented as an old man, flying 
with wings attached to his back ; carrying an hour-glass in one hand, 
and a scythe in the other. These are very appropriate emblems of 
time ; the old man represents time, his flying admonishes us to improve 
every moment as it comes, or it wilL be lost ; the hour-glass reminds 
us that our life, like the sand in the glass, will soon run out ; and the 

scythe, like time, 

" Cuts down all, 
Both great and small." 

Saturn is the 6th lunar planet from the sun, and the most remarka- 
ble ; it is next in order to Jupiter, and the most remote planet from the 
earth, of any that are visible to the naked eye. It may easily be dis- 
tinguished from the fixed stars by its pale, feeble and steady light. It 
is 890 millions of miles from the sun, and revolves around it in 29 
years 167 days ; so that its apparent motion among the stars is very 
slow, being only 12 degrees in a year. Saturn, besides being attended 
with seven moons, is surrounded by. two large concentric rings, which 
are separate from each other, and also from the planet. The matter, 
of which these rings are composed, is undoubtedly no less solid than 
the planet, and they are observed to cast a strong shadow upon the 
planet itself. Saturn, in bulk, is about 1,000 times larger than the 
earth, and revolves on its axis in lOh. 29m. 16s. This rapid motion 
upon its axis, causes it to be, like Jupiter, very much flattened at the 
poles. So that the equatorial diameter is to the polar, as 12 to 11. 
The rings of Saturn present a phenomenon, to which there is nothing 
analagous in the rest of the solar system. These rings are very thin, 
one within the other, and directly over the equator. They revolve 
round in the same time with the planet, although they are detached 
from it. 

The axis of Saturn is inclined to that of it's orbit 28° 40', and as 
the rings are in the plane of the equator, the axis of the rings has the 
same inclination. It will be seen from this, (see Diagram,) that the 
sun shines alternately for 15 years on one side of the rings, and then 
upon the other ; so that if we lived upon the rings, we should have 
continued day for 15 years, and then continual night for the same length 
of time. 

The rings of Saturn must present to the inhabitants of the planet a 
most magnificent spectacle. They appear like vast arches, or semi- 
circles of light, extending from the eastern to the western horizon. At 
the equator, the outer ring is not visible, being hidden from the view 
by the inner ring ; but, in about 45 degrees of latitude, both rings are 
visible, and present a magnificent appearance. During the day-time, 
th^y appear dim like a white cloud, but, as the sun goes down their 
brightness increases; while the shadow of the planet is seen to come 
on at the eastern limb of the ring, and gradually rise to the zenith, 
(see Diagram,) when it passes down and disappears in the western 
horizon at the rising of the sun. The rays of the sun always fall upon 
the sides of the rings very obliquely, as the sun is never seen more than 
30 degrees above the horizon of the rings, while at other times the 
edge of the rings only is presented to the sun. (See Diagram.) These 
rings are rough and of unequal width and thickness, and it has been 
demonstrated that these rings could not maintain their stability of rota- 
tion, if they were in all parts of equal thickness and density, as the 
smallest disturbance would destroy their equilibrium, which would con- 
tinue to increase until at last, they would be precipitated upon the planet. 

Saturn has seven moons, or satellites, but they are only seen with a 
good telescope. Their orbits, with the exception of the seventh, are 
nearly in the plane of the rings ; the seventh, which is the farthest 
from the planet, is the largest, and its orbit is considerably inclined to the 
plane of the rings. (See Diagram.) 



ILLUSTRATED ASTRONOMY 



31 



LESSON XXXI. 
HERSCHEL, OR URANUS. 

Question. When was Herschel or Uranus discovered ? 

Answer. In 1781. 

Q. By whom ? 

A. By Sir William Herschel, who was a celebrated 
English astronomer. 

Q. In what part of the solar system is Herschel situated? 

A. It is the 7th large planet from the sun, and next to 
the farthest discovered. 
Q. What is its magnitude? 

A. It is 80 times larger than the earth. 

Q. What is its specific gravity ? 

A. It is H times the weight of water. (1.53.) 

Q. What is its distance from the sun ? 

A. 1800 millions of miles. 

Q. In what time does it revolve on its axis? 

A. It is not certainly known. [It has been stated at 
1 day 18 hours, but there seems to be no proof of it.] 

Professor Nichol. 

Q. In what time does it revolve around the sun? 

A. In about 84 years. (84y. 6d.) 

Q. How fast does it move in its orbit around the sun ? 
A. 15,000 miles an hour. 

Q. How will the light and heat at Herschel, compare with the same 
at the earth ? 

A. They are 368 times less. 

Q. How many moons has Herschel ? 

A. Six moons were seen by Sir Wm. Herschel, but 
only three have been seen by other astronomers. 

Q. What angle do the orbits, of the two which are best known, 
make with the ecliptic ? 

A. An angle of 78 degrees. (78° 58'.) 

Q. In what direction do these moons move in their orbits ? 

A. They move from east to west, contrary to the mo- 
tions of all the other planets, both primary and 
secondary. 

LESSON XXXII. 
LEVERRIER, OR NEPTUNE. 

Q. When was Neptune discovered ? 

A An 1846, by Dr. Galle, of Berlin. 

Q. Who published the elements of this planet, and directed astrono- 
mers to the point in the heavens where it might be discovered ? 
A. Leverrier, a celebrated French mathematician. 

Q. How near the point, where he directed astronomers to look, was 
it found ? 

A. Within one degree. 
Q. What is the diameter of this planet? 

A. It is about 35,000 miles. 

Q. What is its magnitude ? 

A. It is about 80 times larger than the earth. 

Q. What is its distance from the sun ? 

A. About 2,850 millions of miles. 
Q. In what time does it revolve on its axis ? 
■A. It is not known. 



LEVERRIER, OR NEPTUNE.— Continued. 

Q. In what time does it revolve around the sun ? 
A. In about 166 years. 

Q. How many moons has Leverrier ? 

A. One ; and another is supposed to have been seen. 

Q. What amount of light and heat has this planet ? 

A. About 900 times less than that of the earth. 

Q. Does this planet correspond to the calculations of Leverrier, as to 
mass and distance from the sun ? 

A. Its mass and distance are considerably less than 
his calculations. 

Q. What have these circumstances led some astronomers to suppose ? 

A. That Leverrier is one of a group of planets similar 
to the Asteroids, situated at nearly the same distance 
from the sun. 

Q. Are the primary planets inhabited ? 

A. They appear to be inhabitable. 

[Note. — The presence of clouds indicating both air and water ; the 
regular succession of the seasons, as well as day and night ; the suita- 
ble amount of light received from the sun ; the accompaniment of 
moons ; the specific gravity of bodies at their surface ; all seem to 
indicate that the primary planets are suitable residences for living 
beings. The only objection to this view is, the difference in the 
amount of heat received from the sun, supposing it to be according to 
the inverse ratio of the squares of their distances from the sun. But 
we see from the difference of temperature on the earth, at the base and 
summit of high mountains, that the actual heat depends much upon the 
modifying circumstances, as well as upon the direct rays of the sun. 
And we have reason to suppose that the temperature of the other 
planets does not differ much from that of the earth. 

For instance, the temperature of Mars, as indicated by the melting 
of its snow, and that of Jupiter and Saturn, as indicated by the amount 
of vapor in their atmosphere, appear to be similar to that of the earth. 
Mercury and Venus are protected from (he direct rays of the sun by 
dense clouds. Causes unknown to us, may and probably do, modify 
the temperature of all the planets in a greater or less degree, suffi- 
ciently so, for the purposes of animal life.] 



HERSCHEL. 

This planet was discovered by Sir William Herschel, March 13th, 
1781. It had been . observed by Flamstead, Mayer, Tycho Brahe, 
and other astronomers, and was regarded by them as a fixed star, and 
such it was considered by Dr. Herschel, until he discovered it to be a 
planet, from its having moved from the place where he had observed 
it some time before. 

Sir William Herschel gave it the name of " Georgium Sidvs, or 
Georgian Star," in honour of his Royal patron, George III., but the 
Royal Academy of Prussia, called it Uranus. 



THE NEW PLANET. 

CAUSE WHICH LED TO ITS DISCOVERY. 

It had been found by observation, that the attraction of the planets 
upon each other, accelerate or retard the motion of each. These varia- 
tions have been well understood by astronomers for many years ; but 
it was found by a series of observations made during several years 
upon the planet Herschel, that its motion in the heavens was affected 
by some cause other than that of Saturn or Jupiter. This led astrono- 
mers to suspect that there might be another planet, either between the 
orbits of Saturn and Herschel, or beyond that of Herschel. Leverrier, 
having collected the observations of the most celebrated astronomers for 
many years, was enabled, by his profound knowledge of the mathe- 
matics, to calculate its elements. 



32 



PMAS» 0)1 ' TB MOON 



FULL MOON 



LAST QUARTER 



FIRST O.UARTER 



FIRST QUART* 



rx# 



N EW MOON 



FIC.l 




LAST QUARTER 



FU LL MOON 
OR OPPOSITION 



, NEWMOON OR 
INFERIOR 
CON J UNCTION 



NEW MOON OR 

IN FERIOR 

CO N JUNCTION 



FULL MOON 
OR OPPOSITION 



APOGEE LAST auARTER 



N EW MOON 



X- 



FIRST QUARTER , 



^«t- 




F/1RST QUARTER 



LAST aUARTER 



FIG. 2 
*> R T>y 



)m^m 



FULLMOON 




PERIGEE 



FIG. 3" 






KlOC* AS 3EtN FROM THE EARTH 
.PPEAR-. AS LAHCC AS THE SUN 



ILLUSTRATED ASTRONOMY 



33 



LESSON XXXIII. 
MOON. 

Question. What is the moon ? 

Answer. The moon is a secondary planet, revolving 
around the earth. 

Q. Is the moon larger or smaller than the earth ? 

A. It is 49 times less than the earth. 

Q. What is the diameter of the moon ? 

A. 2,180 miles. 

Q. What is the specific gravity of the moon ? 

A. It is 3h times the weight of water, (3.37.) 

Q. What is its mean distance from the earth? 

A. Two hundred and forty thousand miles. 
Q. In what time does the moon revolve around the earth ? 

A. In about 27 £ days, (27c?. Vi. 43m. 115.5.) 

Q. In what time does the moon revolve upon its axis ? 
A. In about 27<| days, or in the same time that it 
revolves around the earth. 

Q. What is the result of the moon's revolving upon its axis and 
around the earth in the same time ? 

A. The same side of the moon is always presented 
to the earth. 

Q. Have we ever seen the opposite side of the moon ? 
A. We have not. 

Q. What causes the moon always to present the same side to the 
earth ? 

A. It is supposed that one side of the moon is more 
dense than the other, consequently the centre of gravity 
is not in the centre of the moon. 

Q. What is a lunation, or lunar month ? 

A. It is the time from one new moon to another. 

Q. What is the length of a lunation ? 

A. About 29A days. (29d. I2h. Urn.) 

Q. Why is a lunation longer than the time it takes the moon to 
revolve around the earth ? 

A. Because the earth is revolving around the sun at 
the same time. (Fig. 3. See Note 1.) 

LESSON XXXIV. 

Q. What is the length of the days or nights at the moon ? 

A. About 15 of our days. (Note 4.) 

Q. Which way does the moon revolve around the earth ? 

A. From west to east. 

Q. If the moon revolves from west, to east, what causes it to rise in 
the east? 

A. It is caused by the earth's revolving on its axis the 

same way. (Note 2.) 

Q. Does the moon rise the same hour every evening ? 

A. It rises about 50 minutes later every day. 

Q. What is the cause of its rising 50 minutes later every day ? 

A. It is caused by the moon's revolving around the 

earth from west to east. 

Q. What causes the phases of the moon, from new moon to new 
moon again ? 

A. It is caused by the moon's revolving around the 
earth. (See Diagram. Note 3.) 

Q. When is it new moon ? 

A. When the moon is between the earth and sun, 
and the dark side is presented to us. (Fig. 1.) 



MOON.— Continued. 

Q. When is it full moon ? 

A. When the moon is upon the opposite side of the 
earth from the sun, and the illuminated side is pre- 
sented to us. (Fig. 1.) 

Q. How much greater is the light of the sun than the full moon ? 
A. 300,000 times greater. 

Q. When are the sun and moon in quadrature? 
A. When they are ninety degrees distant from each 
other. (Fig. 1.) 

Q. How much of the illuminated side of the moon is visible to us 
when it is in quadrature 7 

A. One-half. (Fig. 1.) 

Q. How much larger is ..he sun than the moon ? 
A. 70 millions of times greater. 

Q. Why does the moon appear as large as the sun ? 
A. Because it is four hundred times nearer to us 
than the sun. (See Fig. 4.) 



Note 1. Fig. 3. — The moon revolves around the earth in about 27-| 
days, but from one new moon to another it is about 29§ days ; this dif- 
ference is caused by the earth's revolving around the sun at the same 
time that the moon is revolving around the earth. This will appear 
plain by examining Fig. 3, on the opposite page. If we suppose the 
moon to be in conjunction or new moon, while the moon is revolving 
around the earth, the earth moves through nearly one-twelfth part of its 
orbit, and when the moon arrives at A, it will have made a complete 
revolution around the earth ; but the moon will not be in conjunction, 
or between the earth and sun, until it has moved the distance from 
A to B — hence it will be seen that from one new moon to another the 
moon has to make more than one complete revolution around the earth. 

Note 2. — That the moon revolves around the earth from west to 
east, from one new moon to another in about 29| days, there is 
not the least doubt ; and it will appear perfectly plain if we consider 
that the earth is revolving on its axis the same way, or from west to 
east ; the earth revolves on its axis in 24 hours, whereas the moon is 
29 £ days in revolving around the earth ; consequently the moon only 
moves from west to east in 24 hours, as much as the earth turns 
on its axis in 50 minutes, which makes the moon rise as much later 
every evening. If the earth did not revojve upon its axis, then the 
moon would rise in the west, and after being above the horizon for 
nearly 15 days, would set in the east, and would be below the horizon 
for the same length of time, when it would rise again in the west. 

PHASES OF THE MOON. 

Note 3. Fig. 1. — By phases of the moon is meant the various ap- 
pearances which the moon presents from new to full moon, and from 
full moon to new moon again. As the moon is a dark body of itself, 
there is only one-half of its surface illuminated by the sun. At new 
moon, when the moon is between the earth and sun ; that side of 
the moon upon which the sun shines, is towards the sun, and the dark 
side is presented to the earth ; consequently we do not see any portion 
of the illuminated side of the moon at new moon, see Fig. 1 ; but as 
the moon passes around from west to east, it brings the illuminated 
side of the moon more and more to our view ; at the first quarter we 
can see one-half of the illuminated surface, and when the moon arrives 
at full moon, we can see the whole of the illuminated surface, as the 
earth is then between the sun and moon. From full moon to new 
moon again, the illuminated surface disappears in the same manner as 
it appeared. 

LENGTH OF THE DAYS AND NIGHTS AT THE -MOON. 

Note 4. As the moon revolves on its axis only once in its revolution 
around the earth, it continually presents the same side to the earth, 
and there would be, consequently, only one day and night in each revo- 
lution of the moon around the earth, or the day and night would each be 
nearly fifteen days long. 



ILLUSTRATED ASTRONOMY 



35 



LESSON XXXV. 
MOON.— Continued. 

Question. Has the moon an atmosphere ? 

Answer. Very little if any. 

Q. What is rhc appearance of the moon when viewed with a teles- 
cope ? 

A. It appears covered with light and dark spots of 
various shapes. 

Q. What is the cause of this appearance ? 

A. It is caused by the mountains, plains and valleys 
in the moon. 

Q What are the light spots ? 

A. Mountains and elevated land. 

Q. What are the dark spots ? 

A. Plains, valleys, &c. 

Q. Has the moon any oceans, seas, or large bodies of water? 

A. Not upon the side towards the earth. 

Q. If you were living upon this side of the moon, what would be the 
appearance of the earth ? 

A. The earth would appear like a large stationary 
moon. 

Q. How much larger than the moon appears to us ? 
A. Thirteen times greater. 

Q. In what time would the heavenly bodies appear to revolve around 
the moon ? 

A. The stars would appear to revolve in 27^ days, 
the sun in 29^ days. 

Q. What is the shape of the moon's orbit 1 
A. Elliptical, or one diameter greater than the other. 
{See Diagram, page 24.) 

Q. What is apogee ? 

A. It is the point in the orbit of the moon farthest 
from the earth. 

Q. What is perigee ? 

A. It is the point in the orbit of the moon nearest 
to the earth. 

Q. When is the moon in apogee ? 

A. When it is at its greatest distance from the earth. 

Q. When is the moon in perigee ? 

A. When it is nearest to the earth. 

Q. Has the moon any change of seasons? 

A. None, except those changes which take place 
every lunar month. 

Q. What is the harvest moon? 

A. When the moon is full in September and Octo- 
ber, it rises only a few minutes later for several suc- 
cessive evenings, and thus affords light for collecting 
the harvest, it is therefore called the harvest moon. 

Q. What is the cause of the harvest moon ? 

A. It is caused by the moon's orbit being very ob- 
lique to the horizon. 

Q. Is the moon inhabited ? 

A. The. want of air and water, render it uninhabit- 
able bv beings like ourselves. 



PHYSICAL CONSTTxTJTION OF THE MOON. 

I?« viewing the moon with the naked eye, .her disc appears diversi- 
fied with dark and bright spots, which on being examined with a pow- 
erful telescope are discovered to be mountains and valleys. The whole 
surface of the moon is covered with these spots, which is evident from 
the fact that the line of separation between the illuminated and dark 
hemispheres, is at all times extremely ragged and uneven. The 
mountains on or near this line cast behind them long black shadows, 
like the mountains on the earth when the sun is rising or setting. The 
moon is a much more mountainous body than the earth, and the moun- 
tains are vastly higher compared with its size than those of the earth. 
One of the mountains {named Tycho) situated in the southeast part of 
the Moon, is apparently a volcanic crater 50 miles in diameter, and 
16,000 feet deep, with a central mountain rising to the height of 
5,000 feet. The height of ten of the principal mountains, according 
to the recent measurement of Maedler, is from 3| to 4| miles. The 
mountains of the moon do not run in ranges like those of the earth ; 
but are single peaks scattered over nearly the whole surface of the 
moon, and are generally of a circular form shaped like a cup. These 
facts substantially prove the mountains of the moon to be of volcanic 
origin, and in some of the principal ones, decisive marks of volcanic 
stratification, arising from successive deposites of ejected matter, may 
be distinctly traced with powerful telescopes — The moon contains no 
large bodies of water, such as, oceans, seas, &c, especially upon the 
side visible to us. If there are any, they must be upon the opposite side 
of the moon which is never presented to us. The moon also has very 
little if any atmosphere, at least, none of sufficient density to refract the 
rays of light in their passage through it : from these two circumstances 
there are no clouds floating around the moon : if there were any, they 
would at times be visible to us, but none have been observed, it pre- 
sents the same appearance that it did 2,000 years ago ; no trace of 
vegetation or change of seasons has been observed, everything appears 
solid, desolate, and unfit for the support of animal or vegetable life. 
Whether the materials of which the moon is composed, are of the 
same nature as the earth, there are no means of knowing. From the 
effect of the moon's gravitation in producing the nutation of the earth's 
axis, the mass of the moon is determined to be very nearly 1.80th of 
the mass of the earth, whence, as her volume is 1.49th of the 
earth's volume, it follows that her density as compared with the mean 
density of the earth is .615 or a little more than one half; consequent- 
ly the materials of which the moon is composed are about half as heavy 
as the same bulk of the earth. 

There being little or no atmosphere about the moon, the heavens, 
in the daytime, have the appearance of night to the inhabitants of the 
moon, when they turn their backs to the sun ; and the stars then 
appear, as bright to them as they do in the night to us ; for it is entirely 
on account of the li^ht which our atmosphere reflects that the heavens 
appear luminous about us in the daytime, If our atmosphere were 
removed, only that part of the heavens would be light in which the sun 
is situated ; and if we turned our backs to the sun the heavens would j 
appear as dark as night. The light which the full moon affords us is 
very small, when compared with the light of the sun ; it being 300,000 
times less. It has also been demonstrated that the light reflected by 
the moon produces no heat ; as its rays, when collected by the aid of 
the most powerful glasses, have not been perceived to produce the 
slightest effect upon the thermometer. 

IS THE MOON INHABITED ? 

From the physical constitution of the moon, it is evident that the 
moon is not inhabited ; at least, by beings constituted like ourselves. 
The moon having no atmosphere, we could not maintain an existence 
upon its surface for a single hour ; even if it is provided with the other 
necessary means for our existence : neverthless, this is not conclusive 
evidence that the moon is not inhabited. The same power that called 
the moon into existence could as easily constitute beings fitted to inha- 
bit its surface, and enjoy an existence like that of ours. It may be 
very properly asked — if the moon is not a habitable body, for what 
purpose was it created ? This is a question which is more easily asked 
than answered. We do know that it exerts a powerful influence m 
raising the tides, and how far this influence operates upon the aninal 
and vegetable kingdoms, we are unable to decide ; its influence ;', no' 
doubt felt to a greater or less extent. 



38 



ILLUSTRATED ASTRONOMY. 



LESSON XXXVI. 
ECLIPSES. 

Question. What is an eclipse ? 

Answer. It is the interception of the sun's rays by 
some opake body. 

Q. How are eclipses divided, with respect to the body eclipsed ? 

A. Into two kinds, solar and lunar. 

Q. What is a solar eclipse ? 

A. It is an eclipse of the sun. 

Q. What is the cause of an eclipse of the sun ? 

A. It is caused by the moon's passing between the 
earth and sun, and casting its shadow upon the earth. 
(Fig. 3.) 

Q. When must an eclipse of the sun take place ? 

A. It can happen only at new moon. 

Q. What is a lunar eclipse ? 

A. It is an eclipse of the moon. (Fig. 3.) 

Q. What causes an eclipse of the moon? 

A. It is caused by the moon's passing through the 
earth's shadow. (Fig. 3.) 

Q. When must an eclipse of the moon take place ? 

A. It can happen only at full moon. (Fig. 3 and 4*) 

( . How are eclipses divided, with respect to the amount eclipsed? 

A. Into total and partial. 

Q. W hat is a total eclipse ? 

A. It is an eclipse of the whole of the sun or moon. 
(Fig. 3 and 8.) 

Q. What is a partial eclipse? 

A. It is an eclipse of only a part of the sun or moon. 

(Fig. 7.) 

Q. What is an annular eclipse ? 

A. It is an eclipse of the central part of the sun, when 
the moon is so far from the earth, that the sun can be 
seen like a bright ring around it. (Fig. 9, Note.) 

Q. Do we have an eclipse of the sun at every new moon ? 

A. We do not. 

Q. Why do we not have an eclipse of the sun at every new moon ? 

A. Because at new moon, the moon is generally too 
high or too low for its shadow to fall upon the earth. 

(Fig. 5.) 

Q. Do we have an eclipse of the moon at every full moon? 

A. We do not ; at. full moon the moon generally 
passes above or below the earth's shadow. 
Q. What is the length of the earth's shadow ? 

A About 600,000 miles. (Note. This is the mean or 
average length.) 

Q. What is the length of the moon's shadow ? 

A. About 234,000 miles. (Note. This is the mean or 
average length.) 

Q. What is a digit? 

A. It is the twelfth part of the apparent diameter of 
the sun or moon's disc. (Fig. 6.) 

Q. What is the greatest number of eclipses that can take place in 
a year ? 
A. Seven ; five of the sun and two of the moon. 

Q. What is the least number of eclipses that can take place in a 
year ? 
A. Two; and both must be of the sun. 



ECLIPSES. 

All opake bodies cast a shadow when the rays from any luminous 
body fall upon them. Every primary and secondary planet in the 
solar system casts a shadow towards that point of the heavens which 
is opposite to the sun. If the sun were smaller than the earth, the 
earth's shadow would increase^ in diameter as the distance increases 
from the earth, (See Fig. 1 ;) but if the sun and earth were of the 
same size, the shadow would be of the same size, no matter how great 
the distance from the earth, (See Fig. 2.) But as the sun is im- 
mensely larger than the earth, the earth's shadow terminates in a point 
at about 600,000 miles from the earth ; the length of the earth's 
shadow is, however, subject to considerable variation. When the 
earth is nearest to the sun, which takes place about January 1st, the 
shadow is much shorter than when the earth is at its greatest distance, 
which is about the 1st of July. The moon revolves around the earth 
in about 29| days, from one new moon to another. If the moon 
passed at every new moon exactly between the centres of the sun and 
earth, we should have a grpat eclipse of the sun at every new moon, 
and a total eclipse of the moon at every full moon, (See Fig. 3 ;) but 
the moon's orbit or path makes an angle with the plane of the ecliptic, 
(the plane of the ecliptic is described by a line drawn from the centre 
of the sun, passing through the centre of the earth and extended to 
the heavens,) of about 5£ degrees, consequently one half of the moon's 
orbit is above the ecliptic, and the other half is below it. 

The two opposite points where the moon's orbit cuts the plane of the 
ecliptic, are called the moon's nodes ; the nodes do not keep in the 
same position with respect to the earth and sun, but have a retrograde 
motion of about 19 degrees in a year. This causes the moon at new 
moon to be too high or too low, so that the moon's shadow passes 
above the north pole or below the south pole, hence there is no eclipse, 
and at full moon, the moon passes either above or below the earth's 
shadow. A total eclipse of the moon occurs when the whole of the 
moon is immersed in the earth's shadow, (See Fig. 3 ;) but we occa- 
sionally have a partial eclipse of the moon which is caused by the 
moon's being so high or so low as only to be partially immersed in the 
earth's shadow, (See Fig. 4.) The diameter of the sun and moon's ; 
discs is divided into twelve equal parts, called digits (See Fig. 6 ;) but 
by inspecting the diagram, it will be seen that when the sun is said to . 
have six digits eclipsed, that only about one third of the disc of the sun 
is covered by the moon, although one half of the diameter of the sun is 
hidden from view. The sun and moon appear to be about the same 
size, but the apparent size of both is subject to some variation : when 
the earth is in that point of its orbit nearest the sun (January 1st,) the 
sun appears larger than at any other time during the year, and, when 
the moon is at the greatest distance from the earth, she appears the 
smallest. If an eclipse of the sun should take place exactly at this 
time, the shadow of the moon would terminate in a point before it reached 
the earth, and the moon would not appear large enough to cover the 
whole disc of the sun, but would produce what is called an annular 
eclipse, or the sun would appear like a luminous ring around the moon, 
(See Fig. 9;) but if the earth was at its greatest distance from the sun 
(July 1st) and the moon the nearest to the earth, then the moon would 
appear larger than the sun, and the shadow of the moon would touch 
the earth before it terminated in a point; this would produce a total and 
as great an eclipse of the sun as can take place, (See Fig. 3.) A 
total eclipse of the sun is visible only to a small portion of the earth at 
one and the same time, the shadow of the moon where it touches the 
earth would be only about 150 miles in diameter, consequently there 
would be only a space across the earth from west to east about 150 
miles wide, in which it would appear total, but, a partial eclipse would 
be seen from a space more than 2,000 miles wide on each side of 
the umbra, or dark shadow. Those who lived north of the dark 
shadow would see the southern portion of the sun eclipsed, and those 
who lived south of it, would see the northern limb of the sun eclipsed. 

Eclipses of the sun are more frequent than of the moon, because 
the sun's ecliptic limits are greater than the moon's, yet we have more 
visible eclipses of the moon than of the sun, because eclipses of the 
moon are visible from all parts of the earth where the moon is above 
the horizon, and are equally great to each of those parts ; but eclipses 
of the sun are visible only to those places upon which the moon's 
shadow falls. 



40 



ILLUSTRATED ASTRONOMY. 



ECLIPSES.— Continued. 
Question. Why are there more eclipses of the Sun than of the Moon ? 

Answer. Because the Solar Ecliptic Limit is 10° 
degrees greater than that of the Moon. 

Q. Are visible eclipses of the Moon more frequent at any particular 
place, than those of the Sun ? 

A. They are ; because an eclipse of the Moon is 
visible and appears as great to all places on the Earth 
where the Moon is above the horizon. 

Q. Why are not visible eclipses of the Sun as frequent as those of 

the Moon ? 

A. Because an eclipse of the Sun is visible only at 
those places on the Earth where the Umbra or Pen- 
umbra falls. 

Q. What is the Umbra of the Earth, Moon or any other planet ? 

A. It is the total dark shadow of the planet, see Fig- 
1, 2, 3, 4. 

Q. What is the Penumbra ? 

A. It is a faint shadow surrounding the Umbra, Fig. 
1, 2, 3, 4. 

Q. What is the extent of the Moon's Umbra upon the Earth when 
greatest ? 

A. It never can exceed 175 miles in diameter, and 
it generally is much less, see Fig. 3. 

Q. Wh}' do eclipses of the Sun always begin on the western side 
of the Sun ? 

A. Because the Moon passes from west to east be- 
tween the Earth and Sun. 

Q. Why do eclipses of the Moon begin on the eastern side of the Moon ? 

A. Because the Moon passes from west to east 
through the Earth's shadow, see Fig. 1. 

Q. In what direction does the Moon's shadow pass over the Earth 
in a Solar Eclipse ? 

A. It passes over the earth from west to east. 

Q. How large a portion of the Earth's surface may be covered by 
the Moon's Penumbra ? 

A. A space about 4,393 miles in diameter. 

Q. Why are not all eclipses of the Sun total? 

A. Because the Moon being so far from the Earth, 
its shadow terminates in a point before it reaches the 
earth, see Fig. 2. 

Q. In what point of its orbit must the Moon be to cause a total 
eclipse of the Sun ? 

A. It must be at or near its perigee, when the Um- 
bra of the Moon would reach the Earth, see Fig. 3. 

Q. How long may an eclipse of the Moon continue ? 

A. It may continue four hours ; in this case the 
Moon must pass directly through the centre of the 
Earth's shadow, see Fig. 1 . 

Q. Is the Moon ever visible when it is totally eclipsed ? 

A. It is, and appears of a reddish color like tarnish- 
ed copper. 

Q. What causes the Moon to be visible when it is totally eclipsed ? 

A. The rays of the Sun in passing through the 
atmosphere of the Earth are refracted or turned out 
of their course and falling upon the Moon render it 
faintly visible. 



Q. What are the effects of a total eclipse of the Sun ? 

A. The heavens are shrouded in darkness, so that 
the stars and planets become visible ; the animal 
tribes become agitated ; and a general gloom over- 
spreads the landscape. 

Q. How long can a total eclipse of the Sun continue at any one 
place on the earth ? 

A. A total eclipse of the Sun cannot continue at 
any one place over four minutes. 

Q. Why is the dark portion of the New Moon visible when seen in 
the west soon after the Sun is set ? 

A. Because the rays of the Sun falling upon the 
Earth are reflected back upon the dark portion of the 
Moon and render it faintly visible, see Fig. 4. [This 
appearance of the Moon at new moon is sometimes 
called " the Old Moon in the New Moon's arms."' 

Q. Are the Stars or planets ever hidden from our view by the Moon ? 

A. They frequently are, which is called the Occul- 
tation of a star or planet. 



ECLIPSES. 

Eclipses are among the most interesting phenomena presented to us by the heavenly 
bodies. In all ages, when an eclipse has taken place, it has excited the profound atten- 
tion of the learned, and the fears and superstitions of the ignorant. The causes of 
eclipses before the seventeenth century were known only to a few, and they generally 
took advantage of this knowledge to impose upon the credulity of the ignorant by pre- 
tending that they were inspired by the Gods. Among the ancient nations, the Chal- 
deans were the foremost in their observations of the phenomena of the heavens ; per- 
haps this was owing in some measure to their occupation ; They being shepherds were 
obliged to watch their flocks by night to protect them from the wild beasts which were 
at that lime numerous. Men under such circumstances would naturally be led to watch 
closely the movements of the heavenly bodies, and more especially so; for in the 
earlier periods of the world they had no correct mode of recKoning time in order to 
determine the seasons or the proper seed time and harvest. 

Eclipses attracted the particular attention of the Chaldeans, and by a series of ob- 
servations extended through several centuries, they discovered a very important fact 
relating to eclipses although they did not understand the cause. 

By comparing the records which had been made for a great length of time, they 
found that a certain period of time elapsed between eclipses of the same kind and 
magnitude ; that is, if 18 years, 11 days, 7 hours and 43 minutes, were added to the 
time of the happening of any eclipse, it would show the time of the return of the same 
eclipse ; the only differences would be that it would not happen at the same time in 
the day and it would be a little greater or less than the previous eclipse — thus they 
were able to predict eclipses with sufficient accuracy to answer their designs upon the 
ignorant without understanding the laws by which these periodical returns were 
produced. 

To explain this briefly, it must be remembered that the moon's orbit makes an angle 
with the plane of the earth's orbit of 5}° ; these two points where the moon's orbit 
cuts the plane of the earth's orbit, are called nodes, (see diagram, greatest number of 
eclipses in one year, page 45). Now we will suppose that on any day at noon it is new 
moon, and the moon is just 16° degrees from her descending node, the shadow of the 
moon would just touch the earth at the north pole ; in 223 lunations or 18 years, 11 days, 
7 hours, 43 minutes thereafter, the moon would come nearly to the same position as it 
was at the beginning, consequently there would be another small eclipse of the Sun, 
and at the expiration of every 223 lunations it would return, and at each return the 
moon's shadow would pass across the earth a little more to the south until the eclipse 
had appeared about 77 times, when it would pass off at the south pole, occupying a 
period of 1388 years : Tiie same period would not commence again until the expiration 
of 12492 years. Each eclipse which takes place during any year, belongs to a separate 
and similar period. Those periods of eclipses which come in at the Moon's ascending 
node, first come on to the earth at the south pole and at each return the moon's shadow 
passes across the earth more to the north and after appearing about 77 times they finally 
leave the earth at the north pole. 

In those periods of eclipses of the moon whicn come in at the moon's descending 
node, the moon first touches the upper portion of the earth's shadow and at each return 
the moon passes through the earth's shadow more to the south and at the thirty-second 
return the moon would pass directly through the centre of the earth's shadow, produc- 
ing a great eclipse of the moon ; also in those eclipses of the moon which come in at 
tne moon's ascending node, the moon first comes in contact with the lower portion of 
the earth's shadow and at each return the moon passes through the shadow more to the 
north and goes through a similar course as in the former case ; it must be remembered 
that there are a number of eclipses in each year, the greatest number is seven the least 
two ; but the eclipses which happen in any one year cannot take place again until the 
expiration of 18 years, 11 days, 7 hours, 43 minutes. 



42 



ILLUSTRATED ASTRONOMY, 



LESSON XXXVII. 

MOON'S NODES. 

Question. What are nodes ? 

Answer. They are two opposite points where the orbit 
of the moon, or any other planet intersects the plane of 
the earth's orbit or ecliptic. 

Q. What angle does the moon's orbit make with the plane of the 
earth's orbit or ecliptic. 

A. About 5) degrees. (5° 8' 48".) 

Q. What part of the moon's orbit is above or north of the plane of 
the earth's orbit ? 

A. One half, the other half being below, or south of 
the earth's orbit ? 

Q. What is the ascending node ? 

A. It is that point where the moon passes the plane 
of the earth's orbit from south to north. 

Q. What is the descending node ? 

A. It is that point where the moon passes the plane 
of the earth's orbit from north to south. 

Q. Do the nodes change their position as regards a fixed point in the 
heavens ? 

A. They have a retrograde motion of about 19 degrees 
in a year. 

Q. When is the moon in north latitude in the heavens? 

A. When it is north of the earth's orbit or ecliptic. 

Q. When is the moon in south latitude in the heavens ? 

A. When it is south of the earth's orbit or ecliptic. 

Q. What is the greatest latitude of the moon ? 

A. 5\ degrees north or south of the earth's orbit or 
ecliptic. 

Q. What is the greatest declination of the moon, or its distance north 
or south of the equinoctial or equator? 

A. About 28i degrees. 

LESSON XXXVIII. 

Q. How near one of the nodes must the moon be at new moon to 
cause an eclipse of the sun? 

A. Within seventeen degrees. (16° 59".) 

Q. How near one of the nodes must the moon be at full moon to 
cause an eclipse of the moon ? 

A. About 12 degrees. (11° 25' 4".) 

Q. If the moon is exactly in one of her nodes at new or full moon, < 
what kind of an eclipse will it cause? j 

A. It will cause a great eclipse of the sun or moon. 

Q. What is the extent of the solar ecliptic limit in which an eclipse 
of the sun can take place ? 

A. Thirty-four degrees, seventeen degrees on each 
side of either node. 

Q. What is the extent of the lunar ecliptic limit in which an eclipse 
of the moon can take place ? 

A. Twenty-four degrees, twelve on each side of 
either node. 

INFERIOR AND SUPERIOR CONJUNCTION. 

Q. How many kinds of conjunction are there? 
A. Two ; inferior and superior. 

0. When is a planet in inferior conjunction with the sun? 
A. When it is between the earth and sun. 



CONJUNCTION.— Continued. 

Q. What planets can be in inferior conjunction ? 

A. Mercury and Venus ; also the moon. 

Q. When are two planets in superior conjunction ? 

A. When they are on opposite sides of the sun. 

Q. What planets can be in superior conjunction with the sun ? 

A. All the planets, except the earth and moon. 
LESSON XXXIX. 

INFERIOR AND SUPERIOR PLANETS. 

Q. How are the primary planets divided ? 

A. They are divided into two classes, inferior and 
superior. 

Q. Which are the inferior planets ? 

A. Mercurv and Venus. 

ml 

Q. Why are they called inferior planets ? 

A. Because their orbits are within the orbit of the 
earth. 

Q. W'hich are the superior planets ? 

A. Mars, " the Asteroids," Jupiter, Saturn, Herschel 
and Leverrier. 

Q. Why are they called superior planets ? 

A. Beca 
the earth 



A. Because their orbits are greater than the orbit of 



HELIOCENTRIC AND GEOCENTRIC LATITUDE AND LONGITUDE. 

Q. W T hat is the Heliocentric latitude and longitude of a planet? 

A. It is its latitude and longitude, as seen from the 
sun. (See Diagram.) 

Q. What is the Geocentric latitude and longitude of a planet? 

A. It is its latitude and longitude as seen from the 

earth. 

Q. Does a planet, seen from the earth, appear to have the same 
longitude as it would have if seen from the sun at thesame time? 

A. It does not, unless the earth is between the sun 
and planet. 



It will be seen by inspecting the diagram upon the opposite page, 
that there are two small circles introduced into the diagram, the white 
circle which represents the moon's orbit, and the shaded circle which 
lies in the plane of the earth's orbit or ecliptic ; this shaded circle is 
introduced into the diagram only to show the two points where the 
moon's orbit intersects the plane of the earth's orbit or ecliptic ; these 
two points are called the moon's nodes ; the point where the moon 
passes from the south to the north side, or above the earth's orbit, is 
called the ascending node ; and the opposite point, or where the moon 
descends below the 1 earth's orbit, is called the descending node ; the 
line passing through the centre of the earth from one node to the other, 
is called the " line of the nodes." It will be seen also that one half of 
the moon's orbit is above the plane of the earth's orbit, and the other 
half below it. 

The planets Mercury and Venus are called inferior planets, because 
their orbits are within that of the earth, and of course nearer to the sun. 
The other primary planets, Mars, Asteroids, Jupiter, Herschel and 
Leverrier, are called superior planets for the same reason that their 
orbits are greater, or outside that of the earth. 

It will be seen by inspecting the diagram upon the opposite page, 
that the planets, seen by two observers at the same time, one upon the 
sun and the other upon the earth, would not appear to be exactly in the 
same point of the heavens. The heliocentric longitude of a planet 
is where it would appear to .be if seen from the sun, and the geocentric 
longitude of a planet is its longitude as seen from the earth. 



44 



ILLUSTRATED ASTRONOMY, 



LESSON XL. 

GREATEST NUMBER OF ECLIPSES IN A YEAR. 

Question. What is the greatest number of eclipses that can take 
place in a year ? 

Answer. Seven ; five of the sun and two of the moon. 

Q, What is the least number of eclipses that can take place in a 
year ? 

A. Two ; both of the sun. 

Q. What must be the position of the moon and her ascending node, 
on the first day of January, to cause seven eclipses in a year? 

A. It must be new moon, and the moon must be 
within 17 degrees of her ascending node at the time. 

Q. When would the second eclipse take place ? 

A. The second eclipse would be of the moon, January 
15th, at her descending node. 

Q. When would the third eclipse take place ? 

A. The third eclipse would be of the sun, January 
29th, at the moon's ascending node. 

Q. When the fourth eclipse ? 

A. The fourth eclipse would be of the sun, June 26th, 
at the moon's descending node. 

Q. When the fifth eclipse? 

A. The fifth eclipse would be of the moon, July 11th, 
at her ascending node. 

Q. When the sixth eclipse ? 

A. The sixth eclipse would be of the sun, July 25th, 
at the moon's descending node. 

Q. When the seventh and last eclipse ? 

A. The seventh eclipse would be of the sun, Decem- 
ber 20th, at the moon's ascending node. 

Q. Why are there no eclipses in this case from January 29th to 
June 26th ? 

A. Because the moon is so hi°;h at new moon that its 
shadow passes above the north pole, and at full moon, 
the moon passes below the earth's shadow. 

Q. Why are there no eclipses in this case from July 25th to Decem- 
ber 20th ? 

A. Because the moon is so low at new moon, that its 
shadow passes below the south pole, and at full moon, 
the moon passes above the earth's shadow. 

Q. What must be the position of the moon and her ascending node, 
on the 1st day of January, to cause only two eclipses during the year? 

A. It must be new moon, and the moon must be in 
or very near her ascending node. 

Q. How often are there seven, or only two eclipses in a year ? 

A. Not oftener than once in a hundred years. 

Q. What is the most common number of eclipses in a year? 

A. Four. 



Greatest Number of Eclipses in a Year. 

When the moon is within 17 degrees of either node at new moon, it 
will cause an eclipse of the sun, and when the moon is within 12 
degrees ofeither node at fiill moon, the moon will then be more or less 
eclipsed. If the line of the noaes were carried parallel to itself around 
the sun. there would be just half a year from the time of one node 
passing the sun, to the other's coming around to the sun ; but as 



the nodes have a retrograde motion of about nineteen degrees in a year, 
it is only 177 days from the conjunction of one node to the conjunction 
of the other, therefore, in whatever time of the year we have eclipses of 
the sun or moon at either node, we may be sure that in 177 days, we 
shall have eclipses about the other node. If we suppose the moon at 
new moon to be 17 degrees from her ascending node on the first day 
of January, there would be a small eclipse of the sun, and at the next 
full moon, January loth, there would be a total eclipse of the moon; as 
the moon would be only about 2 degrees from the descending node ; at 
the next new moon, January 29th, the moon would then be about 12 
degrees upon the other side of the ascending node, which would cause 
another small eclipse of the sun, — hence we would have two small 
eclipses of the sun at the ascending node, and one great eclipse of the 
moon at the descending node, from January 1st to January 29th. (See 
Diagram.) At every subsequent new moon, the moon would be so 
high that the shadow would pass above the north pole, and at every 
full moon, the moon would pass below the earth's shadow, until June 
26th, when the moon's descending node would come around to the sun, 
(see Diagram ;) at this time the moon would be about 7 degrees from 
her descending node ; this would cause another eclipse of the sun. At 
the next full moon, July 11th, there would be another total eclipse of 
the moon ; again, at the next new moon, July 25th, the moon would 
still be within 17 degrees of her descending node, which would produce 
another small eclipse of the sun. 

From July 25th, there would be no eclipses of the sun or moon, as 
at every subsequent new moon, the moon would be so low that the 
shadow of the moon would pass below the south pole, and at every full 
moon the moon would pass above the earth's shadow, until December 
20th, when the ascending node would come around again to the sun, and 
at the 12th new moon in the year, the moon would again be within 17 
degrees of her ascending node ; we would, therefore, have another 
small eclipse of the sun, which would be the seventh and last eclipse 
during the year. It will be seen from the above, that we should have 
five eclipses of the son, and two total eclipses of the moon, during the 
year, which is the greatest number that can possibly take place in a 
year. Seven eclipses in a year do not occur twice in a hundred 
years, although perhaps we may have seven eclipses in one year's 
time, for several times during a century. To have seven eclipses dur- 
ing the same year, it is necessary that the moon and nodes be in a 
particular position on the first day of January. 

After the sun, moon and nodes have been once in a line of conjunc- 
tion ; they return nearly to the same position again in 223 lunations or 
18 years 11 days 7 hours 43 minutes 20 seconds, when four leap years 
are included, or one day less, when five leap years are included ; con- 
sequently, if to the mean time of any eclipse of the sun or moon, we 
add 18 years 11 days 7 hours 43 minutes 20 seconds, we shall have 
the mean time of the return of the same eclipse for a long period of 
time. This period was first discovered by the Chaldeans, by a long 
series of observations, extending through many centuries* and by it 
they were able to foretell, with considerable exactness, the appearance 
of an eclipse, varying at most but a few hours. Every eclipse within 
this period of 18 years, belongs to a separate series of eclipses, that is, 
there is but one eclipse during the 18 years, which belongs to the same 
series. If any series of eclipses commence at the ascending node, the 
shadow of the moon just touches the earth at the north pole ; at the 
next return in 18 years, the shadow will pass across the earth a little 
more to the south, and at each return, the shadow will continue to pass 
more to the south until it will have appeared about 77 times, which 
will take about 1,388 years, when it will pass off the earth at the south 
pole, and at. the expiration of 12,492 years, the same eclipses will com- 
mence again to go through a similar course. Those eclipses of the 
sun which come in at the descending node, the shadow of the moon 
first touches the earth at the south pole, and at each return passes more 
to the north, and finally leaves the earth at the north pole, after having 
appeared the usual number of times. The velocity of the moon's 
shadow across the earth in an eclipse of the sun is about 1.850 miles 
an hour, or about four times the velocity of a cannon ball. The moon 
when totally eclipsed, is generally visible if it is above the horizon, 
and the sky is clear : it generally, appears of a faint dusky r?d, or 
copper color, this is caused by the rays of the sun, which pass through 
the atmosphere of the earth, and are refracted or bent inward, so 
that some of the rays fall upon the moon and render it visible. 



±J 



46 



ILLUSTRATED ASTRONOMY 



LESSON XLI. 

TIDES; 

Question. What motion have the earth and moon, besides revolving 
around the sun ? 

Answer. They revolve around their common centre 

of gravity ? 

Q. In what part of a straight line joining their centres, is the centre 
of gravity situated 1 

. A. About 3,200 miles from the centre of the earth. 

Q. What effect has the centrifugal force upon the water on the oppo- 
site side of the earth from the moon ? 

A. It causes it to recede from the centre of gravity, 
and to rise on that part of the earth. 

Q. What effect has this upon the shape of the earth ? 

A. Its diameter is lengthened in the line of the moon's 
attraction, and shortened at right angles to it. 

Q. What tends to increase this oval shape of the earth ? 

A. The inequality of the attraction of, the moon at the 
different sides of the earth. 

[The water upon the side of the earth nearest to the moon, is more 
attracted than the centre of the earth ; the Water upon the opposite side 
is less attracted.] 

Q. What effect does the turning of the earth, from west to east on its 
axis, produce ? 

A. It causes these elevations, or tide waves, to pass 
from east to west around the earth. 

Q. What is tide ? 

A. It is the rising and falling of the waters of the 
ocean. 

Q. How are the tides divided with respect to the rising and falling 
of the water? 

A. Into flood and ebb. 

Q. What is flood tide ? 

A. It is the rising of the water. 

Q. What term designates the greatest elevation of the flood tide? 

A. High water. 

Q. What is ebb tide ? 

A. It is the falling of the water. 

Q. How often do flood and ebb tide occur ? 

A. Twice in about 25 hours. 

Q. Do the tides rise at the same hour every day ? 

A. They rise about an hour later each day. 

Q. Why do the tides rise later ? 

A. because the moon passes the meridian about an 
hour later each day. 

Q. What causes the moon to be later at the meridian ? 

A. It is caused by its revolving monthly around the 
earth from west to east. 

Q. Does the attraction of the sun produce an effect "similar to that of 
the moon ? 

A. It tends to raise a tide two fifths as high. 

Q. When the sun and moon are on the same or opposite sides of the 
earth, what is the effect of their attractive forces 1 

A. They raise a tide equal to the sum of their separ- 
ate tides, * 

Q. When they are in quadrature, what is the effect of their counter- 
acting forces ? 

A. They raise a tide equal to the difference of their 
tides. ' 



LESSON XLII. 

Q. How are tides divided with respect to their comparative height ? 
A. Into spring and neap. 

Q. What is spring tide 1 

A. It is the greatest flood and ebb tide. 

Q. What is neap tide ? 

A. It is the least flood and ebb tide. 

Q. What proportion do these tides bear to each other ? 

A. The neap tide is about three sevenths as great as 
the spring tide. 

Q. When do spring tides occur ? 

A. Twice in each lunar month, at new and full moon. 

Q. When do neap tides occur? 

A. Twice in each lunar month at the quarters. 

Q. What effect have the continents upon the tide waves when pass- 
ing round the earth ? 

A. They subject them to great irregularities. 

Q. Which side of the continents have the highest tides, the eastern 
or the western ? 

A. The eastern side. 

Q. Does the water remain permanently higher on the east than on 
the west side of the continents ? 

A. The gulf of Mexico is 20 feet higher than the 
Pacific ocean, and the Red sea is 30 feet higher than 
the Mediterranean. 

Q. Where the tide wave is least obstructed, as in the Pacific ocean, 
how much behind the moon is it ? 

A. It is two or three hours behind it. 

Q. How long after the moon passes the meridian, is it high water at 
New York ? • 

A. About 83 hours. 

Q. If the earth were uniformly covered with water, how high would 
the tide rise ? 

A. Not more than tWo or three feet. (The tide at 
the small islands in the Pacific ocean is usually less.) 

Q. What produces the greatest effect in causing high tides ? 

A. The shape of the land, and the position of the 
shores. 

Q. Where are the highest tides in the world ? 
A. In the bay of Fundy. 

Q. What, besides the position of the shores, tends to raise a high 
tide at this place ? 

A. The meeting of the tide wave from the North 

Atlantic ocean, with the main one from the South 

Atlantic. 

Q. How high are the average spring tides at Cumberland near the 
head of the bay of Fundy ? 

A. About 71 feet. 

Q. How high are they at Boston ? 
A. About 11 feet. 

Q. At New York ? 

A. About 5 feet. 

Q. At Charleston, South Carolina. 

A- About 6 feet. 

Q. When do we have the highest tides in the northern hemis- 
phere ? 

A. At new moon in the summer, and at full moon in 

the winter. (See Diagram.) 



1 



si 



NEAP TIDE 



FULL MOON OR 
OPPOSITION 






run. MQOM &\ 




FIRST QUARTER 




spring\tide 




NEW MOON OR 
CONJUNCTION 





5 LAST Q.UARTER 



GREATEST TIDES 
..." IN" THE NORTHERN 
:-•-' HEMISPHERE DURING THE 
DAY AND LEAST DURINO THE NIGHT 



THEMOON VISIBLE IN THE 
NORTH POLAR CIRCLE 1+ DAYS 
IN EACH LUNATION INTHEW/N7ER 



m FULL MOON 



.....— -"GREATEST TIDES IN 
'THE NORTHERN HEMISPHERE 
DURING THE NICHT AND LEAST 
DURING THE DAr 



THEMOON VISIELEINTME SOUTH 
POLAR CIRCLE 1+ DAY'S IS EACH 
LUNATION IN THE SUMMER 



, 



43 



ILLUSTRATED ASTRONOMY 



LESSON XLIII. 
ORBITS OF THE PLANETS AND COMETS. 

Question. What is the orbit of a primary planet ? 

Answer. It is the path in which it revolves around 
the sun. 

Q. What is the orbit of a secondary planet ? 

A. It is the path in which it revolves around its 
primary. 

Q.. What is the form of the orbits of all the planets? 

A. Elliptical, or longer one way than the other. 

Q. Are all the orbits elliptical in the same proportion ? 

A. They are not; some are more elongated than 
others. 

Q. What is the position of the orbits of all the planets? 

A. They extend from west to east in the heavens. 

Q. Do the planes of their orbits, intersect the ecliptic or orbit of 
the earth ? 

A. They do, at small angles. (See Diagram.) 

Q. Do they all intersect the plane of the earth's orbit at one point, 
as represented in the diagram ? 

A. They do not ; but intersect it at different points. 

Q. Through what point does the plane of the orbit, of every primary 
planet and comet in the solar system, pass? 

A. Through the centre of the sun. 

Q. Are the planets at nearly the same distance from the sun ? 

A. Thev are not, but at. very different distances. 

Q. Are their orbits all contained within the zodiac? 

A. They are, except those of a part of the asteroids. 

Q. How wide is the zodiac ? 

A. Sixteen degrees wide : eight degrees on each side 
of the ecliptic. 

Q. Do all the planets revolve around the sun in the same direction ? 

A. They do ; *rom west to east. 

Q. Do they all move with the same velocity? 

A. The velocity decreases as the distance from the 
sun increases. 

Q. Which planet moves in its orbit with the greatest velocity? 

A. Mercury. 

Q. Which moves with the least ? 
A. Leverrier, Or Neptune. 

Q. When does a planet have north latitude ? 

A. When it is above, or north of the earth's orbit. 

Q. When does a planet have south latitude? 

A. When it is below, or south of the earth's orbit. 



LESSON XLIV. 
COMETS. 

(Question. What are comets ? 

Answer. They are bodies which revolve around the 
sun in very elongated orbits. 

Q. How are comets usually distinguished from the planets ? 

A. By a luminous train or tail, on the opposite side 
from the sun. 

Q. Is this luminous train always on the opposite side from the sun ? 

A. Not always; a few have been observed to have 
a different direction. 



Q. Do comets ever appear without a luminous train ? 

A. Some are entirely destitute of any such appendage. 

Q. What is the number of comets ? 

A. The number is not known; about 500 have been 
seen at different times. 

Q. Are comets solid bodies like the planets ? 

. A. They generally are not; although some have been 
observed to have a dense nucleus, or head 

Q. What is the nature of comets? 

A. They are supposed to be gaseous matter, in the 
form of smoke, fog, or clouds. 

Q. Do comets shine by their own, or by reflected light ? 

A. They shine by reflected light. 

Q. Do they all, like the planets, revolve in the same direction around 
the sun ? 

A. They do not ; they revolve in different directions. 

Q. Are all their orbits within the zodiac? 

A. They are not ; their orbits are in all directions in 
the heavens. 

Q. How do many of them move when first seen ? 

A. They appear to move in almost a direct line 
towards the sun. 

Q. Does their velocity increase as they aproach the sun ? 

A. It does; and when near it, they move with im- 
mense velocity. 

Q. How fast has a comet been known to move ? 

A. 880,000 miles an hour. ■ 

Comets. 

Comets were anciently viewed by mankind with astonishment and 
fear, as being forerunners of dreadful calamities, such as war, famine, 
or pestilence. Many ancient philosophers considered them as only 
meteors in the atmosphere. Tycho Brahe was the first who showed 
that they belonged to the planetary system, and revolved around the 
sun. The orbits of all the comets are very elliptical, -so that they 
approach the sun almost in a direct line, and after being involved in the 
light of the sun for a short time, depart from our solar system in nearly 
the same direction, in which they approached, and remain for years, 
or even centuries, beyond the limit of the best telescopes. 

Very little is known of the physical nature of comets ; the smaller 
comets, such as are visible only with telescopes, generally have no 
appearance of a tail, and appear like round or somewhat oval, va- 
porous masses, more dense towards the centre ; yet they have no 
distinct nucleus or solid body. Stars of the smallest magnitude are 
seen through the most dense parts of these bodies. It is very probable 
that the luminous part of a comet is something of the nature of smoke, 
fog, or other gaseous matter. Halley's comet, which appeared in 
1456, with a tail 60 degrees in length, and spread out like a fan, has 
appeared periodically every 77th year, viz : 1682, 1759, and in 1836 : 
but it has exhibited no tail, or luminous appendage, since 1456. The 
comet which appeared 371 years before Christ, is said to have covered 
a third part of the visible heavens. A remarkable comet made its 
appearance 43 years before Christ, and was so bright as to be visible 
in the day time ; it was supposed, by the superstitious, to be the ghost 
of Casar, who had just been assassinated. The following are some 
of the most remarkable comets : — 

Comet of 1680, length of the tail 123,000,000 miles. 
Do. 1744, " " 35,000.000 " 

Do. 1769, " " 48.000.000 " 

Do. 1*11, " " 130.000.000 " 

Do. 1843, " " 130.000.000 



50 



ILLUSTRATED ASTRONOMY. 



COMETS .—Continued. 



Question. What are the principal parts of a comet ? 

Answer. The Nucleus, the Envelope and the Tail. 

Q. What is the Nucleus ? 

A. It is the most dense or solid portion, sometimes 
called the head. (See the comet of 371.) 

Q. What is the Envelope ? 

A. It is a luminous matter surrounding the Nucleus. 

Q. What is the Tail of of a comet ? 

A. It is a long luminous train extending "off from 
the head in the opposite direction from the sun. (See 
Note 1.) 

Q. What effect has the eccentricity of their orhits upon the motion 
of the comets ? (See Note 2.) 

A. Their motion increases as they approach the 
sun and decreases as they recede from the sun. . 

Q. What effect has the change of position upon their appearance? 

A. Their tails usually increase both in length and 
breadth as they approach the sun and contract as 
they recede from the sun. 

Q. Is any thing known of their Temperature ? 

M They must be very hot when near the sun. 
(See Note 3.) 

Q. What can you say of the size of comets ? 

A. Their Nuclei or heads are usually small, being 
only from 33 to 2000 miles in diameter. 

Q. Do all the comets revolve around the Sun continually? 

A. Professor Nichol and Sir John Herschel are of 
opinion that the greater number visit our System but 
once, and then fly off in nearly straight lines till they 
pass the center of attraction between the Solar System 
and Fixed Stars, and go to revolve around suns in the 
far distant heavens. 

Q. How were comets regarded by the ancients ? 

A. As harbingers of famine, pestilence, war and 
other dire calamities. (Note 4.) 

Q. What other fears have been entertained of comets ? 

A. That they might come in collision with our 
globe and dash it to pieces or burn every thing from 
its surface. 

Q. Is there really any danger of a comet striking the Earth ? 

A. It has been determined upon mathematical cal- 
culations that there is not more than 1 in 281,000,000 
of chances for a comet to strike the Earth. 

Q. What would be the effect if a comet should strike the Earth ? 

A. The only effect it would produce, is that it 
might infuse a gaseous matter into our atmosphere 
which might produce disease or death. (Note 5.) 

Q. What is known of the Periodic times of comets ? 

A. The revolution of only four has been determin- 
ed. [Enck's comet, Si years ; Biela's comet, 6! years ; 
Halley's comet, 76 years ; Comet of 1680, 570 years. 



NOTES. 

Note 1. — Comets assume a great variety of shapes ; some appearing like an enor- 
mous fan, others like a long sword or sabre ; but all curved more or less, and concave 
towards the regions from which they come. The Comet of 1744, represented on the 
opposite page, excited great attention. 

Note 2. — The orbits of Comets are very elongated, having their perihelion very near 
the Sun ; (see diagram, page 45,) consequently as they approach the Sun their velocity 
increases rapidly by the increased attraction of the Sun, and when at their perihelion 
they move with immense velocity. 

Note 3. — The Comet of 1680, came within 130,100 miles of the Sun. and must have 
received 28,000 times more light and heat than the earth receives fiom the Sun. Sir 
Isaac Newton calculated the heat of this Comet to be 2,000 times greater than red hot 
iron, and that it would require 2.000 years to cool ; he assumed that the Comet was a 
solid body, which was not the fact. It is a generally conceded fact at the present day 
that the rays of the Sun to produce much heat, must come in contact with solid bodies ; 
and as Comets are of an extremely thin gaseous matter the rays of the Sun m^y pass 
through them without producing much heat, this is more probably the case. We find 
in ascending high mountains that the atmosphere becomes very cold which ought not 
to be the case if the rays of the Sun impart much heat to the atmosphere in their passage 
through it. It is only when the rays of the Sun come in contact with the earth that 
much heat is produced. The density of comets is probably not so great as that of our 
atmosphere and as they have no solid Nucleus or heads, the probability is that com- 
paratively very little heat is produced by their near approach to the Sun. 

Note 4. — The Comet of 1811, was regarded by the ignorant as the precursor of the 
War that was declared in the following spring between Great Britain and the United 
States. In some cases Comets have excited fears that the day of judgment was at hand 
and that the comet was sent to burn up the world. In 1773, M. Delande of Paris an- 
nounced to the Academy that there was great danger of the Comet which was soon to 
appear, striking the earth. It is said that in consequence of this announcement when 
the Comet appeared, many persons of weak minds died of fright. 

Note 5 — A Comet by striking the earth would produce no more effect upon the 
motions of the earth than the clouds do in striking against high mountains ; besides 
our atmosphere would oppose a powerful resistance, being more dense than the comets, 
it is very doubtful, should a Comet strike the earlh that it would penetrate to its sur- 
face ; but it is more probable that it would be retained in the upper portions of our 
atmosphere. It is very probable that comets contain no aqueous vapors ; but are simply 
of a gaseous matter, and it does not follow from this that it would produce any evil con- 
sequences if it should be incorporated with our atmosphere. 



HAS THE EARTH PASSED THROUGH THE TAILS OF COMETS? 

It has been asserted by some astronomers that the Earth has on several occasions 
passed through the Tail of a comet, and in proof of this fact several cases of a singular 
or peculiar kind of Fog have been noticed at several periods. The first of which any 
record is made was that of 1783, it began on the 18th of June and at places very re- 
mote from each other. It extended from Africa to Sweden and throughout North and 
South America. This Fog continued more than a montii. It did not appear to be car- 
ried to different places by the atmosphere ; because in some places it came on with a 
north wind and at others with a south or east wind, it prevailed in the highest summits 
of the Alps as well as in the lowest valleys. The rains which were very abundant in 
June and July did not appear to disperse it in the least. In Languedoo its density was 
so great that the Sun did not become visible in the morning till it was twelve degrees 
above the horizon ; it appeared very red during the rest of the day and might be looked 
at with the naked eye. This Fog or Smoke had a disagreeable smell and was entirely 
destitute of any moisture, whereas most fogs are moist ; besides all this there was one 
remarkable quality in the Fog or Smoke of 1783, it appeared to possess a phosphoric 
property or a light of its own; We find by the accounts of some observers, that it 
afforded even at mid-night a light equal to that of the full moon, and which was suffi- 
cient to enable a person to see objects distinctly at a distance of two hundred yards, 
and to remove all doubts as to the source of this light, it is recorded that at the time 
there was a New Moon. 

Another remarkable Fog in 1831, which excited the public mind in all quarters of 
the globe, resembled so much that of 1783, that the description given of it, applies 
with equal force to that of 1831. 

Now let us look at the facts. It must be acknowledged by all that these Fogs origin- 
ated from some uncommon cause ; now the next question is, to what causes shall we 
attribute the fogs of 1783 and 1831. Some have supposed that they were caused by 
irruptions of Mount Hecla in Iceland, others have advanced the idea that an jmmens£ 
fire ball in penetrating our atmosphere was there but partially ignited, and that torrents 
of smoke were deposited in the higher regions of our atmosphere and finally diffused 
through it. 

These explanations are very unsatisfactory. If the Fogs were actually produced by 
the earth's passing through any portion of a comet, we have no cause of fear from these 
bodies which have been for centuries a terror and dread to mankind generally. We 
will concede that it is the tact that these Fogs were produced by comets until we have 
a better explanation of their origin. 



52 



ILLUSTRATED ASTRONOMY. 



LESSON XLV. 

ATMOSPHERE. 

Question. What is air ? 

Answer. It is an elastic, invisible fluid, which sur- 
rounds the earth. 

Q. Of what, besides air, is the atmosphere composed ? 

A. Of vapor, carbonic acid, and other gases. 

Q. Is the atmosphere of the same density as we ascend from the 
earth ? 

A. It grows thinner or less dense. 

Q. What is the estimated hight of the atmosphere? 

A. About forty-five miles. 

Q. What is the pressure of the atmosphere upon the earth? 

A. Nearly fifteen pounds to the square inch. (14.6.) 

Q. What is the weight of air compared with water ? 

J.. It is 816 times lighter than water. 

Q. The pressure of the atmosphere is equal to a column of water, 
of what height? 

A. Thirty-three feet. 

Q. Of what is air composed ? 

A. Of oxygen and nitrogen gases. 

Q. In what proportions? 

A. Twenty parts of oxygen to eighty parts of nitrogen. 

LESSON XLV I. 
REFRACTION. 

Question. What is refraction ? 

Answer. It. is the deviation of the rays of light from a 

straight line. 

Q. What is astronomical refraction ? 

A. It" is the deviation of the rays of light in their 
passage through the atmosphere. 

Q. What is the cause of this refraction? 

A. It is caused by the increase of the density of the 
atmosphere towards the earth. - 

Q. In what part of the heavens is the light of a body most refracted? 

A. In the horizon. 

Q. What effect does this refraction have upon the sun at its rising 
and setting ? 

A. It makes the sun appear above the horizon when 
it is actually below it. (See Diagram.) 

Q. Does this affect the length of the day? 

A. It makes the day from six to ten minutes longer, 
from sun rise to sun set. 

Q. Is the light of a body refracted when it is in the zenith ? 

A. It is not. (See Diagram.) 

Q. What is twilight j 

A. It is that faint light, seen before the sun rises and 
after it sets. 

Q. What is the cause of twilight ? 

A. It is caused by the atmosphere's reflecting the 
light of the sun. 

Q. Twilight ceases when the sun is, how far below the horizon? 

A. Eighteen degrees. 



LESSON XLVII, 
PARALLAX. 

Question. What is parallax ? 

Answer. It is the difference between the apparent 
and true place of a heavenly body. 



Q. What is the apparent place of a planet ? 

A. It is the place where it appears to be when seen 
from the surface of the earth. 

Q. What is the true place of a planet? 

A. It is the place where it would appear to be if seen 
from the centre of the earth, or centre of motion. 

Q. Where is the parallax of a heavenly body the greatest ? 

A. At the horizon, and decreases to the zenith. 
Q. How are parallaxes divided ? 

A. They are divided into two kinds, diurnal and 
annual parallax. 

Q. What is diurnal parallax ? 

A. It is the apparent .difference in the situation of a 
heavenly body when seen in the zenith and horizon 
of two places at the same time. (See parallax of Mars 
and Moon.) 

Q. What is annual parallax ? 

A. It is the apparent difference in the situation of a 
star as seen from the earth in opposite points of its 
orbit. 

Q. Have the stars been observed to have any sensible parallax ? 

A. A few have been observed to have a small paral- 
lax of a part of a second. (Note. — No parallax has 
been discovered in more than 30 or 40 of them.) 

Q. What is the cause of their having no appreciable parallax? 

A. Because they are at such an immense distance 
from us. 

Q. If the earth's orbit were a solid ring, how large would it appear 
when viewed from the nearest fixed star ? 

A. No larger than a lady's finger ring. 

LESSON XL VIII. 

LIGHT AND HEAT. 

Q. What bodies produce light ? 

A. Luminous bodies. 

Q. Is light a substance thrown off from a luminous body, or is it 
caused by a vibratory motion ? 

A. It is probably caused by the undulations of an 
extremely subtle fluid. 

Q. In what direction are the rays of light thrown off from a luminous 
body? 
A. In straight lines, and in all directions. 

Q. With what velocity does light move? 

A. About 192 thousand miles a second. (192,500.) 

Q. How was this amazing velocity ascertained ? 

A. By observing the eclipses of Jupiter's moons. 

Q. In what proportion do the light and heat of the planets increase 
or decrease ? 

A. In inverse proportion to the squares of their dis- 
tances from the sun. 

Q. Which planet has the most light and heat, and which the least ? 

A. Mercury has the most, and Leverrier the least. 

Q. If a board a foot square be placed one foot from a lighted candle, 
how many feet square would the shadow be upon the wall, nine feet 
from the candle ? 

A. Nine feet square, or eighty-one square feet. 

Q. What amount of light and heat would fall upon the one foot and 
upon the 81 feet ? 

A. The same amount of light and heat would fall upon 
each. 




THE LIGHT AND HEAT OF THE PLANETS INCREASE OR DECREASE 
IN PROPORTION TO THE SQUARE OF THEIR DISTANCES FROM THE 
SUN .« 



IF THE EARTHS ORBIT WAS A SOUO RINu II 



FINGER RINC.WHEN SEEN FROM 



THE FIXED STARS 



54 



ILLUSTRATED ASTRONOMY, 



LESSON XLIX. 
TERRESTRIAL AND CELESTIAL GLOBES. 

Question. What is a globe ? 

Answer. A globe is a round body or sphere. 

Q. How many kinds of globes are there used in astronomy ? 
A. Two; terrestrial and celestial globes. 

Q. What does the terrestrial globe represent ? 
A. It represents the earth. 

Q. What are drawn upon the surface of the terrestrial globe? 

A. Continents, islands, mountains; oceans, seas, rivers, 
republics, kingdoms, empires, &c. 

Q. What does the celestial globe represent ? 

A. It. represents the heavens as seen from the earth. 

Q. What are usually drawn on the celestial globe ? 
A. The constellations or stars, galaxy or milky way, 
and the figures of various animals and objects from 
which the constellations are named. 

Q. What is a constellation ? 

A. It is a group of stars, to which is applied the name 
of some animal or object. 

Q. What is the number of constellations ? 

A. Ninety-three. 

Q. In viewing the terrestrial globe, where is the observer supposed 
to be placed ? 

A. On its surface. 

Q. In viewing the celestial globe, where must the observer suppose 
himself to be placed? 

A. In the centre, looking towards the heavens. (In- 
side looking out.) 

Q. What is the galaxy or milky way ? 

A. It is a luminous belt forming a complete circle in 
the heavens. 

Q. Of what is the galaxy or milky way composed ? 

A. It is a vast number of stars, so far distant from us, 
and situated so nearly in the same direction, as to 
appear like a thin cloud. 

Q. What is the position of the milky way in the heavens? 

A. It extends from northeast to southwest through 
the whole circumference of the heavens. 

Q. What are the celestial poles, or poles of the heavens? 

A. They are the points where the earth's axis, if 
extended, would meet the heavens. 



LESSON L. 

Question. What does the plane of the equator form, when extended 
to the heavens ? 

Answer. The equinoctial or celestial equator. 

Q. At what angle do the ecliptic and equinoctial intersect each other? 

A. At an angle of 23l degrees. (23° 28' ) 

Q. What does the plane of a meridian form when extended to the 
heavens ? 
A. A celestial meridian or circle of declination. 

Q. What are measured on celestial meridians ? 
A. Declination and polar distance. 

Q. What is the declination of a heavenly body? 

A. It is its distance from the equinoctial, north or south. 

Q. To what are the declination and polar distance always equal ? 

A. They are equal to 90 degrees, or a quarter of a 
circle. 

Q. What is the right ascension of a heavenly body ? 
A. It is its distance east of the first point of Aries 
measured on the equinoctial. 



Q. What angle expresses the right ascension ? 

A. The angle between the meridian passing through 
the body, and the one passing through the first point of 
Aries. 

Q. How far is, right ascension reckoned ? 

A. 360 degrees, or quite round the heavens. 

Q. What are circles of latitude on the celestial globe ? 

A. They are great circles which pass through the 
poles of the ecliptic, and cut its plane at right angles. 

Q. What is the latitude of a heavenly body? 

A. It is its distance north or south of the ecliptic, 
measured on a circle of celestial latitude. 
Q. What is the longitude of a heavenly body? 

A. It is its distance east of the first point of Aries, 
measured on the ecliptic. 

Q. What angle expresses the longitude ? 

A. The angle between the circle of latitude passing 
through the body, and the one passing through the first 
point of Aries. 

Q. Where is this angle formed ? 

A. At the poles of the ecliptic, where the circles of 
latitude intersect each other. 

Q. How far is celestial longitude reckoned? 

A. It is reckoned 360 decrees. 



LESSON LI. 

Question. What is a vertical circle ? 

Ansiver. It is a great circle in the heavens, passing 
through the zenith and nadir, and cutting the horizon 
at right angles. 

Q. What vertical circle is the meridian ? 

A. It is that vertical circle which passes through the 
north and south points of the horizon. 

Q. Which is the prime vertical ? 

A. The vertical circle which passes through the east 
and west points of the horizon. 

Q. What are measured on the vertical circles ? 

A. Altitude and zenith distance. 

Q. What is the zenith distance of a heavenly body? 

A. It is its distance from the zenith. 

Q. To what are the altitude and zenith distance always equal ? 

A. They are equal to 90 degrees. 

Q. What is the azimuth of a heavenly body? 

A. It is its distance east or west of the meridian. 

Q. What angle expresses the azimuth ? 

A. The angle between the meridian and the vertical 
circle passing through the body. 

Q. M hat is the amplitude of a heavenly body? 

A. It is its distance nprtii or south of the prime vertical. 

Q. What angle expresses the amplitude ? 

A. The angle between the prime vertical, and the 
vertical circle passing through the body. 

Q. Where are the angles expressing azimuth and amplitude formed? 

A. At the zenith where the vertical circles intersect 
each other. 

Q. On what circle are these angles measured ? 
A. On the horizon. 

Q. To what are azimuth and amplitude always equal 1 

A. They are equal to 90 degrees. 

[The diagram can be used to illustrate azimuth, amplitude, altitude, 
and zenith distance, by supposing the ecliptic to represent the celestial 
horizon, and the circles of celestial latitude to represent vertical circles.] 



56 



ILLUSTRATED ASTRONOMY. 



LESSON LII-. 

THE FIXED STARS. 

Question. What are those stars called which always appear to be 
in the same situation with respect to each other? 

Answer. They are called the fixed stars. 

Q. What are the fixed stars supposed to be ? 

A. They are supposed to be suns like our own, with 
planets revolving around them. 

Q. Are the stars luminous or opake bodies ? 

A. They are luminous bodies. (Astronomers have no 
doubt on this point.) 

Q. Are all the stars of the same magnitude as the sun? 

A. They are not; some are larger, and others no 
doubt smaller than the sun. (Note 1.) 

["From the orbital motion of the double star 61 Cygni, compared 
with its distance, Bessel has concluded that the conjoint mass of its two 
individuals is 'neither much more nor much less than half the mass of 
our sun.' From the photometric experiments of Wollaston, on a (Al- 
pha] Lyras, compared with what we know of its distance, its actual emis- 
sion of light may be gathered to be not less than 5^ times that of the 
sun. Sirius, which is nine times as bright as a Lyrae, and whose 
parallax is insensible, cannot, therefore, be estimated at less than 100 
suns." Edinburgh Revieu;] 

O. What is the distance of the nearest fixed star, a (Alpha) Centauri? 

A. It is so far distant that a cannon ball going 500 
miles an hour, would take four millions of years to 
reach it. 

Q. What is the number of stars whose distance is imperfectly known 
to us ? 

A. About 35 ; seven of which have their distances 
determined with considerable certainty. 

Q. Do all the stars remain of the same brilliancy? 

A. They do not; some exhibit a periodical change in 
their light. 

Q. What is supposed to be the cause of this change in their light? 

A. The revolution on their axes is supposed to pre- 
sent, alternately to us, sides of different brightness. 

Q. What are those stars called which appear to be surrounded by a 
thin atmosphere ? 

A. Nebulous stars. 

Q. Do stars ever disappear, or new ones become visible ? 

A. Thirteen stars have disappeared, and ten new 
ones become visible, during the last century. (Note 2.) 

Q. What is supposed to be the cause of their disappearance ? 

A. They have probably ceased to be luminous. 

Q. How do astronomers account for the appearance of new stars? 

A. Opake bodies may have become luminous, or new 
suns may have been created. 

LESSON LIII. 

Question. What do the milky way and the single stars that are visi- 
ble to the naked eye, including our sun, constitute? 

Ansiver. They constitute an immense cluster, or fir- 
mament, entirely distinct from the other clusters or 
nebulae of the heavens. (Fig. 1.) 

Q. What is the shape of this great cluster or firmament ? 

A. It has the form of a wheel or burning-glassl 



[The stars extend much farther in the direction of the plane of the 
milky Avay, than fliey do at right angles to it. See Diagram.] 

Q. What is the number of stars in our cluster? 

A. They have been variously estimated from 10 to 
100 millions. 

Q. By what term do some astronomers designate our cluster or 
firmament ? 

A. They call it the unit jrse. (Note 3.) 

Q. Do the fixed stars have any apparent motion ? 

A. They do, but it is so slight as not to be easily 
detected. 

Q. Around what, are all the stars in our cluster, including the sun, 
supposed to revolve ? 

A. Around th' common centre of gravity of the 
cluster. [Fig. 1.) 

Q. Wha' group of stars is thought to be near the centre of the 
cluster ? 

A. The Pleiades, or seven stars. (Dr. Maedler.) 

Q. In what part of the cluster is the solar system situated ? 

A. It is comparatively near the centre. 

Q. How far from us is the centre of the cluster supposed to be? 

A. About 150 times the distance of the nearest fixed 
star. 

[Light is about 8 minutes in coming from the sun ; about 3£ years 
in coming from the nearest fixed star, u Centauri ; about 500 years in 
coming from the supposed centre of the cluster; and about 5,000 years 
in coming from the most remote stars in the cluster.] 

Q. How long will it take the sun to revolve around this centre of 
gravity ? 

A. About twelve millions of years. 

Q. What other motion have some of the stars, besides around the 
centre of the cluster? 

A. Multiple stars, consisting of two or more, revolve 
likewise around their common centre of gravity. 

Q. What is the number of these multiple stars? 

A. About 6,000 have been observed. 

Q. Do these stars appear double to the naked eye ? 

A. They do not; the most, require a good telescope 
to separate them. 

Q. When multiple stars consist of but two, what are they usually 

called ? 

A. Double stars, or binary systems. 



Note 1. — Astronomers, until recently, considered all the stars to be of about the same magni- 
tude, and probably as large as the sun ; and that the stars of the first magnitude owed their bril- 
liancy to their being nearer to us ; but it has been found that the brightest star (Srarca) in the whole 
heavens, and which was considered to be the nearest fixed star, is at a much greater distance 
than some of the smaller stars. This clearly demonstrates that they ar« of very unequal mag- 
nitude. 

Note 2. — There are now seven or eight well-attested cases of fixed stars suddenly glowing for a 
time with such brilliancy as to be Tisible in the day time, through the intensity of their light ; then 
gradually fading away, and becoming entirely extinct. Laplace thinks that some great conflagra- 
tions, produced by extraordinary causes, have taken place on their surface. 

Notk 3. — The term universe, was until recently used to denote the whole creation ol God, and 
was never used in the plural number : but astronomers use the term to denote an immense firma- 
ment or clusterof stars, entirely distinct from other clusters — of which there are many thousands 
visible with the telescope — and are at an immense distance from each other. Hence in speaking 
of these clusters, they call them universes. — [Prof. Mitchell.] 



u 



BINARY^ or DBUBliE STM|S> ; : 

Thes&Stcws receive around, a>ccm,7n,pn> (>egb-0e>. of Grgcv.Lby bzlween, the7TL,^ii£t^^jj^cpr Singly, wi-li/s 

"viewed, wilA cbMg&cjL Telescope^ . , ° ■■-■*' ;i 



I CROWN ORION LION NORTHSTAR • BOOTES HERCULES .VIRGO CRE CCT 3 E l\ R CR EY HOU ND S HARP 



Cd'-ci'.n: t Jl.'&c£ ' I M&on,i,s -. Pglc. 



nfit'afi* \jias^4lpel/ii\ T/£ryin.ius . I JWi^ 



-Hi?ivrbds '' Zy 




58 



ILLUSTRATED ASTRONOMY 



LESSON LIV. 
NEBULA. 

Qxiestion. What appearance has a nebula? 

Answer. A nebula appears like a spot of pale light 
seen in the heavens. 

Q. Of what are the nebulae composed ? 

A. The most of them are great clusters of stars, so far 
distant as to appear like a thin cloud. 
Q. Are there many of them ? 

A. About 6,000 have been discovered. (Note. — Their 
number is probably much greater; perhaps infinite.) 

Q. What is the distance to these nebulae ? 

A. Some of them are said to be so far distant, that 
light, traveling 192 thousand miles a second, would 
not reach us in less than 30 millions of years. [Prof. 
Mitchell.] 

Q. Are they visible to the naked eye ? 

A. Only a few are seen without a telescope. 

Q. How large do they appear when viewed with a telescope ? 

A. Some of them appear as large as one tenth of the 
disc of the moon. 

Q. Are these nebulae «een in all parts of the heavens? 
A. They are, although they are more numerous in a 
narrow zone, circumscribing the heavens, at right 

angles to the milky way. 

Q. Into how many classes may nebulae be divided? 

A. Into five classes, viz., resolved nebula?, resolvable 
nebulae, stellar nebulae, irresolvable and planetary 
nebulae. 

Q. What are resolved nebulae? 

A. They are those which have been discovered with 
the telescope to be great clusters of stars. 

Q. What are resolvable nebulae ? 

A. They are those which are considered to be com- 
posed of stars, but. are so far distant that the telescopes 
have not as yet resolved them. 

O. What are stellar nebulae? 

A. They are those of an oval or round shape, increas- 
ing in density towards the centre. (Note. — They 
sometimes present the appearance of having a dim star 
in the centre.) 

Q. What are irresolvable nebulae ? 

A. They are those which are considered to be lumi- 
nous matter in an atmospheric state, condensing into 
solid bodies like the sun and planets. 
Q. What are the planetary nebulae ? 

A. They are those which resemble the disc of a pla- 
net, and are considered to be in an uncondensed state. 
Q. Are all nebulae beyond our cluster ? 

A They are, except the milky way, and nebulous 

stars. 

Q. By what general term do astronomers designate each nebula or 
cluster ? 

A. They call each nebula a Universe, or Firmament. 

Q. What can you say of the great nebula in the Greyhounds? 

A. It resembles our own cluster, or firmament of 

stars. 

Q. What can you say of the great nebula in Orion ? 

A. This nebula was considered to be luminous mat- 
ter in an uncondensed state, but it has lately been dis- 
covered to be stars by Lord Rosse, with his powerful 



telescope. (Note. — This nebula is visible to the 
naked eye.) 

Q. What is the probable cause of many of the nebulae appearing 
elliptical or elongated? (See Diagram.) 

A. It is probably caused by the edge of the nebula 
being turned more or less towards us. 

ORIGIN OF THE SOLAR SYSTEM. 

Mawy theories hare been propounded at different periods of the history of Astronomv, respecting 
the original formation of our Solar System, as well as all other suns and systems, which it has 
pleased the great creator of all thiscs to call into existence, but no one has gained so great 
favor or excited so violent opposition, as the theory first proposed by Sir William Herschel. and 
afterwards more especially applied by the celebrated La Place to the formation of the solar system 

This theory may he thus stated :— In the beginning all the matter composing the sun. planets, and 
satellites, was diffused through space, in a state of exceedingly minute division, the ultimate parti- 
cles being held asunder by the repulsion of heat In process of time, under the action of gravita- 
tion, the mass assumed a round or globular shape, and the particles tending to the centre of gravity, 
a motion of rotation on an axis would commence The great mass, now gradually cooling and con- 
densing, mil ; increase its rotary mot on. thereby increasing the centrifugal force at the equator of 
the revolving mass.until, finally, a ring of matter is actually detached from the equator, and is left 
revolving in space by the shrinking away from it, of the interior mass If now we follow this iso- 
lated ring of matter, we find every reason to believe that its particles will gradually coalesce into a 
globular form, and in turn form satellites, as it was itself formed It is unnecessary to pursue the 
reasoning further, for the same laws which produce one planet from the equator of the central 
revolving mass, may produce miny — until finally, the process is ended by a partial solidification of 
the central mass, so great, that gravity aided by the attraction of cohesion, is more than sufficient 
to resist the action of the centrifugal force, and no further change occurs 

It has been urged in favor of this theory, that it accounts for the striking peculiarities which are 
found in the organization of the solar system. That the rings of Saturn are positive proofs of the 
truth of the theory, they having cooled and condensed without breaking That the individuals con- 
stituting a system thus produced, must revolve and rotate as do the planets and satellites, and in 
orbits of the precise figure and position, as those occupied by the planets. It accounts for the rota- 
tion of the sun on its axis, and presents a solution of the strange appearance connected with the sun 
called the Zodiacal Light It goes further arid accounts for the formation of single, double, and 
multiple suns and stars— and by the remains of chaotic matter in the interstices between the stars, 
and which are finally drawn to some particular sun. whose influence in the end preponderates, 
accounts for the comets which enter our system from every region in space 

In support ol this theory it has beer, urged that the comets, in their organization, present us with 
specimens of this finely divided nebulous or chaotic matter — and that the telescope reveals cloudy 
patches of light of indefinite extent, scattered throughout space, which give evidence of being yet 
unformed and chaotic. That many stars are found in which the bright nucleus or centre is sur- 
rounded by a halo or haze of nebulous light, and that round nebulous bodies are seen with the tel- 
escope of an extent vastly greater than would fill the entire space encircled by the enormous orbit 
of the planet La Verrier. or having a diameter greater than 7000 millions of miies. 

Such are a few of the arguments in support of this most extraordinary theory We now present 
the objections which have been most strongly insisted on The retrograde motions of the satellites 
of Herschel. and their great inclination to the plane of the ecliptic cannot be accounted for by this 
theory. That computation shows that no atmosphere of uncondensed nebulous matter can extend 
to so great a distance from the sun, as does the matter composing the Zodiacal Light, and, finally, 
that the nebulous matter in the heavens will ultimately be resolved into immense congeries and 
clusters of stars, whose great distance has hitherto defied the power of the best instruments. 

In reply to the first objection, the friends of the theory doubt the facts with reference to the satel- j 
lites of Herschel They reply that the matter composing the Zodiacal Light, being in the nature ' 
of cometary matter, is thrown to a greater distance from the sun than gravity would warrant, bv I 
that power residing in the sun which is able on ttie approach of comets to project those enormous 
trains of light, which sometimes render them so wonderful. As to the last objection, it is urged 
that although many nebula; will doubtless be resolved into stars, by using more powerful teles- ' 
copes, yet that these same telescopes will reveal more new nebula; which cannot be resolved, than ! 
they will resolve — and as to the existence of nebulous matter, it is perfectly demonstrated by the i 
physical organization of comets,^ and the existence of nebulous stars 

Such was the state of the Astronomical argument, w 7 hen Lord Rosse's Great Reflector was first 
applied to the exploration of the distant regions of space. In a religious point of view, this theory 
had excited no small amount of discussion, in consequence of its supposed Atheistical tendencies. 
The friends of the theory contend that it was no more Atheistical to admit the formation of the 
universe by law, than to acknowledge that it is now sustained by laws. Indeed since we must go 
to the first great cause for matter in its chaotic, state, as well as for the laws which govern matter, 
that this theory gave to us a grander view of the omniscience and omnipotence of (Jod than could 
be obtained from any other source. In fine that it harmonized with the declaration of scripture, 
which tells us that " In the beginning God created the heavens and the earth, and the earth was 
without form and void." If the earth came into existence in its present condition, then it had form 
and wasnot void. Hence, this first grand declaration of the inspired writer must refer to the forma- 
tion of the matter, of which the heavens and earth were afterwards formed. Some went so far as 
to trace out dimly a full account of this theory in the order ol creation, as laid down in Genesis. 

Let us now proceed to the discoveries of Lord Rosse. and their influence on this greatly disputed 
theory. The space penetrating power of his six feet reflector is much greater than that of Sir 
William Herschel's great telescope, and it was anticipated that many nebula? which were unre- 
resolved into clusters of stars by Herschel. would yield under the greater power and light of Lord 
Rosse's telescope. This has proved to be the fact Very many nebulae have been removed from 
their old places, and must hereafter figure among the clusters, while we are informed that many 
yet remain, even of the old nebulre, which defy the power of the monster telescope 

The most remarkable object which has been resolved by Lord Rosse. is the great nebula in 
Orion, one of the most extraordinary objects in the heavens. (See Diagram.) Its size is enormous, 
and its figure very extraordinary In certain parts adjoining the nebula the heavens are jet black. 
either from contrast or by the vacuity of these regions. Two immense spurs of light are seen to 
project from the principal mass of the nehula. and to extend to a most extraordinary distance. This 
will be better understood, by remembering that at the distance at which this nebula is removed 
from us, the entire diameter of the earth's orbit, 190 millions of miles, is an invisible point, less than 
one second, while this nebula extends to many thousands of times this distance, and more probably 
to many millions of times. 

Several stars have been found, and are visible on the nebula, but have hitherto been regarded as 
being between the eye of the observer and this remote object. Sir William Herschel was unable 
to resolve this mysterious body, and yet the nehula gave indications of being of the resolvable 
kind, by its irregular and curdled appearance under high powers. Several years since Dr. J. 
Lamont. of Munich, after a rigid scrutiny of this nehula with his great Refractor, pronounced a 
portion of it to be composed of minute stellar points, and predicted its final perfect resolution into 
stars by greater power This prediction has been fully verified, for Lord Rosse's great Reflector 
has solved the mystery, and filled this extraordinary object with the "jewelry of stars" 

But the question recurs, what have the defenders of the nebular theory lost, or its enemies 
gained by this interesting discovery? We are all liable to reach conclusions too hastily, and to 
join issue on false points If the nehular theory depended for its existence upon the iriesolvahilitj 
of the nebula in Orion, then indeed has the theory been entirely exploded But this is not the fact 
No one has asserted that the great nehula in Orion was ndndoiis matter, and if it were not, then 
none existed Such an issue would have been a false one. had it been made 

The theory has neither lost nor gained by the discoveries thus far made ; what time may devel- 
ope it is impossible to sav In case certain data can be obtained, which appear to he accessible, 
then indeed may we demonstrate its truth or falsehood, by mathematical investigation Until 
then, the safer plan is neither to adopt nor reject, but investigate until absolute truth shall reward 
our long continued labor, and reveal the mystery of the organization of that stupendous system, of 
which our hu'nble planet forms an insignificant part 



59 



XEBULAE or CLUSTERS of STARS atanlMMENSE DISTANCE BETOKD OUR CLUSTER, 

The 'Stars Shown, ittlfusc figures have nv cr-nnecT„ion with. iheNelmlac biflMonp tc ourcnn Cluster . 

Resolved Nebulae 




Stellar and Resolvable Nebulae 




Double Nebulae 



Hollow Nebulae 



60 



ILLUSTRATED ASTRONOMY, 



DESCRIPTION AND USE OF THE SIDEREAL MAPS. 



These Maps have been drawn by the Author with great care, in 
order to insure perfect accuracy in their representations of the heavens 
at the times specified in the annexed tables. They have been con- 
structed to show the sidereal hemisphere visible on the parallel of lati- 
tude and meridian of New York (City.) To insure the greatest amount 
of accuracy, the stereographic projection has been made use of, because 
of all projections that occasions the least possible disarrangement of the 
relative positions of the stars and the angles they form one with ano- 
ther. There is a difficulty in reducing a concave or globular surface to 
a plane without distortion taking place somewhere ; and in the projec- 
tion here adopted a little compression will be found, gradually increasing 
from the horizon to the centre of the map. The constellations near the 
zenith will be found to be somewhat smaller, and the stars nearer 
together, than when near the edge of the ma| or horizon. Several 
stars often appear in the heavens, so as to form a group, presenting 
the appearance of a triangle, a rhomboid, trapezium or parallelogram : 
these figures are more correctly preserved by this projection than by 
any other which might have been made use of. The centre of each 
map represents the zenith on the parallel of New York, or that point 
in the heavens directly over the observer's head at the time specified in 
the annexed tables. They will answer equally well for any place 
within the United States, by making an allowance for the situation of 
the place north or south of the parallel of New York. For instance, to 
an observer at Washington the zenith, as represented on the maps, 
would be about 3£° degrees to the north of his zenith ; also, to an 
observer at New Orleans the zenith of the maps would be about 12° 
degrees to the north : at Quebec the zenith of the maps would be about 
6° degrees to the south ; but to all places in the New England, Middle, 
and Western States, the variation would be so small that it would 
hardly be perceptible, unless by accurate observation. As we go north 
or south eur sidereal hemisphere is continually changing. If we go 
north new stars seem to emerge from the northern horizon, while those 
near the southern horizon disappear below it ; ana if we should conti- 
nue our journey to the north pole, we should find the north star in the 
zenith, or directly over head, and that the stars visible to us did not rise 
nor set, but described circles around the north star every 24 hours ; 
these circles increasing in diameter, according to the distance of the 
star from the north star. To a person thus situated, the equator would 
be in the horizon, and he would see none of the stars in the southern 
hemisphere. If there were inhabitants at the south pole they would be 
similarly situated with regard to the stars in the southern hemisphere ; 
they would never see the stars on the north side of the equator or in the 
northern hemisphere, nor would the stars in the southern hemisphere 
ever set to them. To the inhabitants at the equator, the whole of the 
stars, from pole to pole, would rise and set perpendicularly to their hori- 
zon once in every 24 hours. As the equator has no latitude, so has 
its zenith no declination, because the celestial equator is directly over 
it on a line from east to west. If an observer moves towards either 
pole from the equator, for every degree of his progress his zenith will 
have just so many degrees of declination, and as many degrees can he 
see beyond the pole towards which he is advancing ; and he will lose 
sight of the pole from which he is receding in the same proportion. 
For example, as the inhabitants of New York are situated near 41° 
degrees north of the equator, their zenith is elevated 41° degrees above 
the celestial equator ; and it follows that the inhabitants on the paral- 



lel of New York can see all the stars within 49° degrees south of the 
equator — for 41° added to 49° makes 90° — the distance from the zenith 
to the horizon ?* also between the zenith of New York and the north 
pole, are 49° degrees ; requiring 41° degrees beyond the pole to make 
up the complement of 90 degrees ; consequently the stars 41° degrees 
beyond the north pole never set to the inhabitants living on the parallel 
of New York, but describe circles, or appear to revolve around the pole 
star every 24 hours. 

EXPLANATIONS, SHOWING THE MANNER OF 
USING THE MAPS. 

The pupil should be particularly instructed in the manner of using 
these maps, or they will be inclined to use them in the same manner 
as they do the maps of a Geography or Atlas, which will confuse and 
confound them. In using a geographical map the pupil is instructed to 
face the north, and lay the map before him ; then the top represents the 
north, the right hand east, <kc. : but it will be observed, that if this 
mode be adopted with these maps, the right hand represents the west 
and the left hand the east. Each map is intended to represent the 
whole visible heavens at the time given for observation ; hence, if we 
face the south, and hold the map up over the head, with the pole star 
directed towards the north star in the heavens, it will then represent 
nearly the condition of the heavens. In viewing the stars south of our 
zenith, face the south, and hold the map up in front of the eye ; but in 
viewing the stars to the north of our zenith, face the north, turn the 
map bottom upwards, and hold it so that the pole star on the map shall 
correspond with the pole star in the heavens, then the stars on the map 
will indicate the positions of the stars in the heavens. In viewing the 
stars to the east, face the east, and hold the map up before the eye, with 
the top turned towards the north ; the map will then indicate the correct 
positions of the stars : also, in viewing the stars to the west, face the 
west, and hold the map up before the eye, with the top turned towards 
the north. Great care should be taken when an observation is made, 
so as not to mistake the planets Venus, Mars, or Jupiter, for fixed stars. 



DIRECTIONS FOR FINDING THE NORTH STAR, 

AT ANY TIME. 

Every pupil should be instructed in the manner of pointing out the 
North Star at any time of the night. If they are enabled to do this at 
any time, it will assist them in making other important observations, as 
well as being of use on many occasions which occur in the life of every 
man. Many persons have been lost in a prairie or other unfrequented 
places, when if they had been able to have told the points of the com- 
pass they could have extricated themselves from their lost situation. 
This may be done in a very easy manner. There is hardly a child of 
10 years of age who cannot at any time of night point out the stars in 
the Great Bear which form what is called the Great Dlbper. Now 
if an imaginary line be drawn through the two stars which form the 
front edge of the Dipper, from the bottom towards the top, and continued 
about 20° degrees, it will pass very near the North Star — so near that 
it cannot be mistaken, there being no other stars of that magnitude 
near it. It should be borne in mind that this rule holds good in what- 
ever position the Dipper may be at the time. 



ILLUSTRATED ASTRONOMY 



01 



PRINCIPAL CONSTELLATIONS VISIBLE, FROM JANUARY 21 TO APRIL 17. 



Ursa I&ajor, the Crreat Bear. — The first seven stars in 
this constellation form what is called the Great Dipper. It is situated 
about 15 degrees north of the zenith, and a little to the east of north. 
It is exactly bottom upwards, with the handle towards the east. There 
are four stars which form the dipper, and three in the Tail of the Bear, 
which form the handle. These stars cannot fail to be recognized at a 
glance. Six of these stars are of the second and one of the third mag- 
nitude. The first two, a, /?., are called pointers, as a line drawn 
through them towards the horizon would pass very near the North Star, 
which is about 30 degrees from them towards the horizon. 

Ursa Minor, the Little Bear. — The stars in this constella- 
tion form a figure calied by some a Wagon, and by others the Little 
Dipper. It is north of the Great Dipper and east of the North Star, 
which is in the end of the handle. The North Star is at the end of the 
tail of the Little Bear. 

Taurus, the Bull. — The star a, or Aldebaran, is one of the first 
magnitude, and is in the right eye of the Bull ; hence, it is sometimes 
called the Bull's Eye. This constellation is situated nearly west, and 
about 20 degrees above the horizon. The cluster of stars on the head 
of the Bull is called the Hyades. There is a small cluster of stars on 
the neck of the Bull, and north of the word Taurus on the map. It 
consists of seven stars, very near together. This group is called the 
Pleiades, or Seven Stars. Six of these stars only are visible to the 
naked eye. 

Orion. — This is one of the most remarkable constellations in the 
heavens, and was familiarly known to the ancient writers, Job and 
Homer. It contains two stars of the first magnitude, Betelgeuse on 
the right shoulder, and Rigel on the left foot, of Orion. Half way 
between these two stars are three stars in the girdle, in a right line, 
forming Jacob's Staff, or the Three Kings, as they are sometimes called. 
There is a large nebula seen in this constellation, or rather through 
it, as the nebula is at an immense distance beyond the stars. Accord- 
ing to fable Orion was a mighty hunter, who accompanied Diana and 
Latona in the chase. 

Gemini, the Twins. — The two principal stars in this constella- 
tion arc («) Castor and ((?) Pollux ; one in the head of each Twin. 

Canis Minor, the Little Dog. — This constellation contains 
two large stars, («) or Procyon, of the first, and ((?) Mirza, of the third 
magnitude, besides several small stars. This constellation was said 
to be one of the hounds of Orion. 

Canis Major, the Great Dog. — This constellajon is to the 
southeast of Orion, and contains the star Sinus, the brightest star in 
the whole heavens. This is said by the Greeks to be one of Orion's 
hounds — but the Egyptians, no doubt, gave it the name of dog, from 
the fact that it gave them Avarning of the approach of the inundation of 
the waters of the Nile. When this star was seen in the direction of 
the source of the Nile they moved back from the river upon the high 
ground — and as the dog was ever watchful to announce the approach 
of danger, they gave the same name to this star, which they fancied 
warned them, although silently, of approaching danger. 

Leo Major, the Great Lion. — The principal star in this con- 
stellation is («) or Regulus : it is on the meridian at the time for 
observation, and about 30 degrees south of the zenith. There are 
several bright stars in this constellation. The stars in the head and 
neck form a curve somewhat like a sickie, Regulus being in the end of 
the handle. This Lion was supposed to be a metamorphosis of the 
Nemsean Lion, which was slain by Hercules. 

Bootes, the Herdsman. — This is a very large constellation, 
southeast of the Great Bear. The principal stars are (a) Arcturus, of 
the first magnitude, and (?) Izar of the second magnitude. This star is 
situated in the Belt of Bootes. This constellation is of great antiquity; 
so much so that it is doubtful from whence it derived its name. Bootes 



is represented as walking, holding in his right hand a spear, and in his 
left the leading cords of the two dogs Asterion and Chara, which seem 
to be barking at the Great Bear. 

Virgo, the Virgin. — This constellation is east of Leo. The 
principal star is («) Spica, of the first magnitude, in the ear of corn, 
which the Virgin holds in her left hand, and is the^pnly bright star in 
this constellation. The position of this star has been determined with 
great exactness for the benefit of navigators. It is situated within the 
zone, in the heavens traversed by the moon. The moon's distance 
from the star is used for determining the longitude at sea. According 
to the ancient poets, this constellation represented the virgin Astrcea, the 
goddess of Justice, who lived upon the earth during the golden age ; but 
being offended at the wickedness of mankind, during the brazen and 
iron ages of the world, she returned to heaven, and was placed among 
the constellations of the zodiac, with a pair of scales (Libra,) in one 
hand and a sword in the other. 

Corvus, the Crow. — This is a small constellation south of the 
virgin. It contains four bright stars, forming a trapezium or irregular 
square. The brightest of the two upper stars, on the left, is called 
Algorab, in the east wing of the crow. The crow, it was said, was 
once of the purest white, but was changed to black, its present color, as 
a punishment for tale bearing. 

Corona Borealis, the Northern Crown. — This is a small 
constellation between the head of Bootes and Hercules. It may be 
distinguished by six principal stars, which form a circular figure, resem- 
bling a wreath or crown. This beautiful cluster of stars was said to 
be in commemoration of a crown presented by Bacchus to Ariadne, 
the daughter of Minos, second king of Crete. 

Draco, the Dragon. — This constellation coils its fore part around 
the pole of the Ecliptic, and its tail around the Pole Star. In conse- 
quence of its various windings, perhaps it may be found difficult to be 
traced. According to fable, Draco, the offspring of Typhon, with a 
hundred heads and as many voices, was the guardian of the golden 
appies that grew in the garden of Hesperides. He was slain by Her- 
cules, who obtained the apples, and presented them to Eurystheus. 

Canes Venatici, the Grey Hounds. — This constellation con- 
tains only small stars. These two hounds, which Bootes leads with a 
small cord, are named Asterion and Chara. 

Coma Berenices — Berenices Hair. — This is a small constel- 
lation between the Greyhounds, on the north, and the Virgin, on the 
south. It contains only small stars. 

Crater, the Cup. — This cup is south of the Great Lion, and 
east of the Crow. It contains seven stars, so situated as in some 
degree to resemble the outline of a cup. According to fable, Jupiter 
sent the Crow with a cup to fetch water; but the bird being of. a 
vagrant disposition, wasted his time, and returning without the water, 
told Apollo that the stream was guarded by a venomous serpent. To 
punish the Crow for this falsehood, Apollo placed him opposite the cup, 
and commanded the serpent never to allow him to drink. 

Hydra, the Water Serpent.' — This is a very long constella- 
tion, extending over 100 degrees from west to east. It may be known 
by four small stars south of the Crab, and nearly west of Regulus. 
This was supposed to be the Lernaean Hydra, which Hercules slew. 

Sextans, the Sextant. — This constellation was formed by 
Hevelius of stars not included in the other adjacent constellations. It 
contains only small stars. 

Argo Navis, the Ship ArgO. — This constellation is in the south- 
ern horizon. The head of the ship may be known by a small cluster 
of stars about 15 degrees of the dog star Sirius. The greater part 
of this constellation is below the horizon. Some said this was the cele- 
brated ship in which Jason and his companions went to Colchis, in 
quest of the golden fleece, which had fled from Greece. Others main- 
tained that the ship Argo was no other than the Ark of Noah. 



62 



ILLUSTRATED ASTRONOMY 



MAP, FROM JANUARY 21 TO APRIL 17. 

[ fzSP* The Stars and Constellations upon this Map will occupy the exact positions in the heavens as they are laid down 
on the Map, at the times for observations, as specified in the table. The centre of the Map represents the zenith of New- 
York, or any place situated upon the parallel of latitude of 41° north. By occasional observations with these Maps, the 
pupil will become familiar with all the Stars of the first magnitude as well as the principal Constellations. The great advan- 
tage these Maps have over all others, is, that they show the whole visible heavens at the time given for observations, and the 
exact positions of the Stars from the observer as well as from each other. For example : — On the 21st of January, at 1 
o'clock 40 minutes in the morning, the Stars occupy the same positions in the heavens as laid down on the Map. The Star 
Regultjs, of the first magnitude, will be exactly on the meridian, and about 26° degrees south of the zenith ; Procyon, or 
the Little Dog, about 3-5° degrees west ot Regultjs ; and Sirius, or the Great Dog, southwest of Procyon, and near the 
horizon. In this manner the pupil will be able to trace out the principal Stars and Constellations with facility. There are 
many Sectional Maps published, but they are all subject to this one great objection — which is, the great difficulty the pupil 
has in locating it. This objection is entirely obviated in these Maps.] 



STARS OF THE FIRST MAGNITUDE. 



NAMES OF THE CONSTELLATIONS AND PRINCIPAL STARS. 

LEO, The Lion — (Regulus, the principal star.) — This star is 
26° south of the zenith, and on the meridian at the times specified in 
the Table for Map No. 1. 

VIRGO, The Virgin — (Spica.) — This star is southeast, and about 
20° above the horizon. 

BOOTES, The Herdsman — (Arcturus.) — This star is situated 
nearly east, and about 40° from the horizon. 

LYRA., The Harp — (Vega.) — This star is nearly northeast, and 
near the horizon. 

CYGNUS, The Swan— (Deneb.)— This star is about 22° east 
of north, and very near the horizon, and perhaps not visible unless 
the atmosphere is very clear, and the observer situated upon an emi- 
nence. 



AURIGA, The Charioteer — (CapeHa.) — This star is nearly 
northwest, and about halfway from the zenith to the horizon. 

TAURUS, The Bull — (Aldebaran.) — This star is in the eye 
of the Bull, and nearly west, and about 20° above the horizon. 

ORION, Orion — (Betelgeuse.) — This star is in the right shoul- 
der of Orion, a little south of west, and about 30° above the horizon 

ORION, Orion— (Rigel.)— This star is in the left foot of Orion, 
southwest of Betelgeuse, and very near the horizon. 

CANIS MINOR, Little Dog — (Procyon.) — This star is situa- 
ted southwest, about 45° degrees from the horizon. 

CANIS MAJOR, Great Dog — (Sirius.)— This star is southwest 
of Procyon, about 20° from the horizon. This is the brightest star in 
the heavens, and was considered the nearest ; but late observations 
have demonstrated to the contrary. 



TABLE OF THE TIMES FOR OBSERVATIONS, 

SHOWING THE DAY AND HOUR OF THE NIGHT WHEN THE STARS OCCUPY THE POSITIONS INDICATED ON THE MAP. 







H. 


M. 


JANUARY 


21 


1 


40 


» • • • 


22 


1 


36 


■ * • • 


23 


1 


32 


■ • * • 


24 


1 


28 


• • • • 


25 


1 


24 


• • • • 


26 


1 


20 


• • • • 


27 


1 


16 


»-•••» 


28 


1 


12 


• • ■ • 


29 


1 


8 


»».-■« 


30 


1 


4 


• • • • 


31 


1 


— 


FEBRUARY 


1 


12 


56 


• • • • 


2 


12 


52 



3 
4 
5 
6 
7 
8 
9 
10 12 



12 48 



11 



12 44 

12 40 

12 36 

12 32 

12 28 

12 24 
20 

12 16 



h. 



M. 



FEBRU.* 


,RY 12 


12 


12 


• • • • 


13 


12 


8 


• • • • 


14 


12 


4 


• • • * 


15 


12 


— 


• • • • 


16 


11 


56 


• • • • 


17 


11 


52 


• • • • 


18 


11 


■ 48 


• • • • 


19 


11 


44 


■ • • • 


20 


11 


40 


• • • • 


21 


11 


36 


• • • • 


22 


11 


32 


• • • • 


23 


11 


28 


• • • • 


24 


11 


24 


• • • • 


25 


11 


20 


• • • • 


26 


11 


16 


• • • • 


27 


11 


12 


• • > • 


28 


11 


8 


MARCH. 


... 1 


11 


4 


• • • • 


2 


11 


— 


• • » • 


3 


10 


56 


• • • • 


4 


10 


52 


■ • • • 


5 


10 


48 



H. 



M. 



MARCH 6 10 44 

7 10 40 



8 


10 


36 


9 


10 


32 


10 


10 


28 


11 


10 


24 


12 


10 


20 


13 


10 


16 


14 


10 


12 


15 


10 


8 


16 


10 


4 


17 


10 


— 


18 


9 


56 


19 


9 


52 


20 


9 


48 


21 


9 


44 


22 


9 


40 


23 


9 


36 


24 


9 


32 


25 


9 


28 


26 


9 


24 


27 


9 


20 







H. 


M. 


ARC 


^H... 28 


9 


16 




29 


9 


12 


... 


30 


9 


8 




31 


9 


4 


PRII 


u 1 


9 


— 


. . . 


2 


8 


56 


. . • 


. . 3 


8 


52 


... 


4 


8 


48 


• * • 


5 


8 


44 


« » • 





8 


40 


. . . 


7 


8 


36 


• • • 


8 


8 


32 


• • • 


9 


8 


28 


. . . 


10 


8 


24 


. . . 


11 


8 


20 


• • • i 


12 


8 


16 


. . . 


13 


8 


12 


. . . 


14 


8 


8 


. . . . 


15 


8 


4 


• • • * 


16 


8 


— 





17 


7 


56 



64 



I L L IT S T RATED ASTRONOMY 



AN EXPLANATION OF LEAP-YEAE. 



It has been found by observations, that the earth revolves on its 
axis 365^ times nearly, while it is making one complete revolution 
around the sun, or while the sun moves from either equinox to the same 
equinox again ; consequently the solar year, upon which the seasons 
depend, contains nearly 365^ days. It will be seen from this that the 
difference between a year of 365 days and the year as measured by the 
sun, amounts to one day in every four years; so that in 120 years of 
365 days, the seasons would fall back one whole mflnth, or 30 days, 
and the season for May would be in June, and the season for June 
would be in July, &c. In 720 years the longest days would be in the 
month of December : but in about 1450 years the season would fall 
back through the twelve months, and would again correspond to their 
present arrangement. In order to keep the seasons to the same 
months, and to make the solar and civil year correspond, one day more 
is included in the month of February, every fourth year. This would 
always keep the solar and civil year together, if the earth revolved upon 
its axis exactly 365^ times while it was revolving around the sun, or 
durin^ the solar year; but the earth revolves from one equinox to the 
same again in 365 days, 5 hours, 48 minutes, 49 seconds; which is 11 
min. 11 sec. less than 365^ days: consequently, in allowing one day 
in every four years is allowing 44 min. 44 sec. too much ; and in 132 
years it would amount to 24 h. 36 min. 6 sec, or more than one day : 
so that the longest day, which is now on the 21st of June, would, in 132 
years, be on the 20th of June, or one day earlier, and in 264 years the 
longest day would be on the 19th of June, and soon. 

This mode of reckoning time, by making every fourth year a leap- 
year, was adopted by the Council of Nice, in the year of our Lord 325, 
when the longest day in the year happened June 21st, and the vernal 
equinox March 21st. This mode of reckoning was continued from the 
year 325, to 1752, a period of 1427 years ; when it was found that the 
longest day was on the 10th of June, and the vernal equinox on the 
10th of March ; the vernal equinox having fallen back II days towards 
the beginning of the year. To restore the equinoxes to the same days 
of the month in which they happened in the year 325, eleven days 



were ordered, by the British Government, and the United States, then 
British colonies, to be stricken, out of the mouth of September, 1752, 
by calling the 3d day the 14th ; and it was ordered that hereafter one 
leap-year in every 132 years, or 3 leap-years in 400 years, should be 
omitted : that is, that the years 1700, 1800, and 1900, which by the 
Old Style would have been leap-years, should be common years of 
365 days. This method gives 97 leap-years in every 400 years. 
Thus 400 multiplied by 365, plus 97 days for the leap-years, gives 
146,097 days. This divided by 400 years makes 365 days 5 h. 49 min. 
12 sec. ; making a difference from the true solar year of only 23 
seconds a year ; an error which amounts only to one day in 3,866 
years. 

This new arrangement is called the New Style. 

This change was made to keep the equinoxes and solstices to the 
same days of the same months, and to keep the time of celebrating 
Easter, and the other feasts, fasts, and holydays of the Episcopal 
Church, to the same seasons of the year. The Russians and some other 
eastern nations continue the Old Style at the presen' .my. The year 
1800 wa« not a leap year by the New Style, but would have been by 
the Old Style : t .e difference between the styles is now 12 days. 



RULE FOR ASCERTAINING WHAT YEARS ARE 

LEAP-YEARS. 

Divide the years by 4, and if there is no remainder it is Leap- 
Year ; if there is 1 remainder, it is the 1st year after the leap-year; 
if there is 2 remainder, it is the 2d ; if there is 3 remainder, it. is 
the 3d year after leap-year. The even centuries are leap-years only 
when, by cutting off the two cyphers, you can divide the other two 
figures without a remainder. Thus 19(00 is not divisible by 4 without 
a remainder — consequently it is not a leap-year. The years 2,000, 
2.400, 2,800, &c. are leap-years; and 2,100, 2,200, 2,300, 2,500, 
2,600, and 2,700 are not leap-years. 



EQUATION 0E TIME. 



It is observed that time, as measured by the sun, differs from that 
shown by a clock that keeps true and equal time : the, solar day, or 
time from the sun's leaving the meridian of any place till he leaves the 
same again, being sometimes less than 24 hours, and sometimes more ; 
that is, if by a true clock, on any day, the sun leaves the meridian of 
any place at just 12 o'clock, it is either a few seconds before or a few 
seconds after 12, when he leaves that meridian the next time : it is a 
few more seconds, either before or after 12, when he leaves that meri- 
dian again ; and so on, till in a few weeks it is several minutes before 
or after 12 by the clock when the sun leaves the meridian. 

It is, in fact, the place, and the meridian of the place, that leaves the 
sun ; but we say the sun leaves the meridian, because by the motion of 
the earth round its axis, the sun appears to move round the earth every 
day ; and by the motion of the earth round the sun, the sun appears to 
move in the ecliptic round the earth once a year. The motion of the 
earth round its axis is always uniform and equal, never faster at one 
time than at another; this is the only perfectly uniform and equal mo- 
tion known : and the mean or average time of its revolution from the 
sun to the sun again is 24 hours; that is, the averane or mean time 
from the sun's leaving the meridian of any place, till he leaves the 
same again, is 24 hours ; though, as before said, it is sometimes more 
and sometimes less. 

The difference between the time of the sun's leaving the meridian, 
and 12 o'clock, by a true clock, is called The Equation of Time : at 
greatest it is 16 min. 15 sec. ; this is on the last of October, and first 
of November. On the 14th of April, 15th of June, 31st of August, and 
23d of December, this equation or difference is nothing, as then the 



sun and clock agree ; and these are the only days in the year on which 
the sun and clock do agree. 

The Equation depends on two causes ; — viz. 1. The unequal mo- 
tion of the sun in the ecliptic ; — And, 2. The obliquity of the ecliptic 
to the equator. 

It has already been shown that the sun, as well as the moon, moves 
much slower when in or near its apogee, than when in or near its peri- 
gee ; and that its true place is never the same as its mean place, except 
in apogee and perigee. Now as the motion of the earth round its axis 
on the side next the sun, is in the same direction as the apparent motion 
of the sun in the ecliptic, it is plain that the slower the sun moves, the 
sooner will any place on the earth's surface move round from the sun 
to the sun again ; or the shorter will be the solar day ; because as the 
earth revolves round its axis, any place on the earth's surface will over- 
take the sun in less time when he advances through a less space, than 
when he moves through a larger. 

The first equation depends upon the sun's distance from the perigee 
or perihelion, and is the difference between the mean and true place -f 
the sun, changed into time. It is greatest when the sun is half u ,y 
between the aphelion and perihelion, and nothing when it is in the 
aphelion or perihelion. The sun is faster than the clock whil^ it 
is moving from the aphelion to the perihelion, and slower, while is 
moving from the perihelion to the aphelion. This difference, between 
the sun and clock, when greatest, is 7 min. 42 sec. 

The second equation, depending upon the obliquity of the ecliptic 
to the equator, at greatest, is 9 min. 53 sec. — (Spofford's Astronomy, 
page 29.) 

. 1 



ILLUSTRATED ASTRONO M Y . 



05 



PRINCIPAL CONSTELLATIONS VISIBLE, FROM APRIL 18 TO JULY 2L 



Corona Borealis, the Northern Crown, — This constella- 
tion is about 15 degrees southwest of the zenith. Six of the principal 
stars form a circular figure resembling a wreath or crown. 

Bootes, the Herdsman. — This constellation is situated west of 
the Crown. The principal star is Arcturus. 

Hercules. — This constellation is east of Corona or the Crown, 
and extends from 12 to 50 degrees, north declination. It contains one 
hundred and nineteen stars — one of the 2d magnitude and one of the 3d 
in the right shoulder. These are called Beta and Gamma. The left 
or east arm of Hercules grasps the three headed monster Ceuberus. 

According to mythology, this constellation is intended to immortalize 
the name of Hercules, the Theban, so celebrated in antiquity for his 
heroic valor and invincible prowess. By command of Eurystheus, he 
achieved a number of enterprises, the most difficult and arduous ever 
known, called the Twelve Labors of Hercules. 

1st. He subdued the Nemaean Lion in his den, and clothed himself 
in his skin. 

2d. He slew the Lern^iaw Hydra, with a hundred hissing heads, 
and dipped his arrows in the gall of the monster, to render their wounds 
incurable. 

3d. He took alive the stag with golden horns and brazen feet, which 
was famous for its incredible swiftness, after pursuing it for twelve 
months, and presented it unhurt to Eurystheus. 

4th. He took alive the Erimanthean Boar, and killed the Centaurs 
which opposed him. 

5th. He cleansed the stables of Augias, where 3,000 oxen had been 
confined for many years. 

6th. He killed the carnivorous birds which ravaged the country of 
Arcadia, and fed on human flesh. 

7th. He took alive, and brought into Peloponnesus, the wild bull of 
Crete, which no mortal durst look upon. 

8th. He obtained for Eurystheus the Mares of Diomedes, which lived 
on human flesh, after having given their owner to be first eaten by 
them. 

9th. He obtained the girdle of the Queen of the Amazons, a formida- 
ble nation of warlike females. 

10th. He killed the monster Geryon, king of Gades, and brought 
away his numerous flocks, which fed upon human flesh. 

11th. He obtained the Golden Apples from the Garden of Hespe- 
rides, which were watched by a dragon. 

12th. He finally brought up to the earth the three headed dog Cer- 
berus, who guarded the entrance to the infernal regions. 

Lyra, the Harp. — This is a small but beautiful constellation. It 
contains (a) Vega, one of the brightest stars in the northern hemis- 
phere, and is situated directly east, and between 30 and 45 degrees 
from the zenith. 

It is asserted that this is the celestial Lyre which Apollo or Mer- 
cury gave to Crpheus, and upon which he played with such a masterly 
hand, that even the most rapid rivers ceased to flow ; the wild beasts 
of the forest forgot their wildness, and for the time being became tame, 
and the mountains came to listen to his song. 



Aquila, the Eagle. — This constellation may be easily found by 
three stars in a right line ; Altair, of the first magnitude, midway 
between the other two. 

This constellation is supposed to have been Merops, a king of the 
Island of Cos, who was transformed into an Eagle, and placed among 
the constellations. 

Delphinus, the Dolphin. — This is a beautiful little cluster of 
stars, and may be easily distinguished by four principal stars in the 
form of a diamond. The Dolphin was made a constellation for persuad- 
ing the goddess Amphitrite, who had made a vow of perpetual celibacy, 
to become the wife of Neptune. 

Ophiuchus, the Serpent Bearer. — This constellation is repre- 
sented as a man with a long beard, holding in his clenched hands a 
prodigious Serpent, which is writhing in his grasp. This constellation 
occupies a large space, from 15° north to 25° south of the equator. 
The principal star is Ras Alhague, of the second magnitude, situ- 
ated in the head. The star on the foot just south of the ecliptic is 
Rho. According to mythology, Ophiuchus or Esctjlapius, as he was 
sometimes called, was the god of Medicine. He was the son of Apollo, 
but was killed by Jupiter with a thunderbolt, for restoring Hippolytus .o 
life. 

Scorpio, the Scorpion. — This is one of the constellations of 
the zodiac. It is a very beautiful group, as it contains one star of the 
first, two of the second, and eleven of the third magnitude, (a) An- 
tares, of the first magnitude, is situated in the heart of the Scorpion. It 
is a little east of the meridian, and about 20 degrees above the horizon. 
Orion, a celebrated giant, having impiously boasted that there was no 
animal on earth which he could not subdue, Diana, whom he had 
offended, sent a Scorpion, which stung him to death. 

Serpens, the Serpent. — This constellation is united with that 
of Ophiuchus, who holds the serpent in his grasp. It may be distin- 
guished by several bright stars in and near the head 

Libra, the Scales. — This constellation contains 4 stars of the 
2d magnitude, by which it may be distinguished ; two of them being 
about 10 degrees northwest of Antares in the Scorpion. About twenty- 
two hundred years ago this constellation coincided with the sign Libra 
of the ecliptic, and when the sun entered this constellation the days and 
nights were equal ; hence it was very appropriately represented by the 
ancients by a pair of scales, which denote equality. 

Scutum, or Sobieski's Shield. — This is a small constellation, 
instituted by Hevelius. It may be known by three small stars in 
the form of a triangle. 

Vulpecula et Anser — (The Fox and Goose.) — This constel- 
lation was also established by Hevelius, and is situated south of .he 
Swan and north of the Dolphin and Eagle. It contains only small 
stars. 



vo 



ILLUSTRATED ASTRONOMY 



MAP, FROM APRIL 18 TO JULY 21. 

[fdF 3 The Stars and Constellations upon this Map will occupy the exact positions in the heavens as they are laid down 
on the Map, aX the times for observations, as specified in the table. The centre of the Map represents the zenith of New- 
York, or aa v jlace situated upon the parallel of latitude of 41° north. There will be eight stars of the first magnitude visi- 
ble, the most conspicuous of which will be Arcturus, Vega, Altair, Deneb, Antares, and Spica. The other two being near the 
horizon, may not be visible unless the atmosphere is very clear.] 



STARS OF THE FIRST MAGNITUDE. 



NAMES OF THE CONSTELLATIONS AND PRINCIPAL STARS. 

BOOTES, The Hbrdsmaw — (Arcturus the principal star.) — 
This slar is situated towards the southwest, and about 30° from the 
zenith 

VIRGO, The Virgin — (Spica.) — This star is almost in a direct 
line southwest of Arcturus, and about 30° above the horizon. 

LYRA, The Harp — (Vega.) — This star is due east and about 37° 
from the zenith. 

LEO MAJOR, The Great Lion — (Regulus.) — This star is due 
west, and about 10° above the horizon — perhaps not visible unless the 
atmosphere is very clear. 



AQUILA, The Eagle — (Altair.) — This star is nearly southeast 
of Vega, and about half way from Vega to the horizon. 

CYGNUS, The Swan — (Deneb.) — This star is nearly northeast 
of the zenith and east of the North Star. 

AURIGA, The Charioteer — (Capella.) — This star is about 
16° west of north, and veiy near the horizon ; perhaps not visible. 

SCORPIO, The Scorpion — (Antares.)— This star is nearly 
south, being only about 20° east of the meridian. It is about 30° 
above the southern horizon. There are two stars of the second magni- 
tude about 10° to the northwest of it. 



TABLE OF THE TIMES FOR OBSERVATIONS, 

SHOWING THE DAY AND HOUR OF THE NIGHT WHEN THE STARS OCCUPY THE POSITIONS INDICATED ON THE MAP. 







H. 


M. 


RIL. . . 


.. 18 


2 


16 


■ „•'• 


19 


2 


12 


• • • 


20 


2 


8 


• a • 


21 


2 


4 


• • « 


22 


2 


— 


• • • 


23 


1 


56 


• • • 


24 


1 


52 


• • • 


25 


1 


48 


■ • • 


26 


1 


44 


• • • 


27 


1 


40 


• • * 


28 


1 


36 


• • * 


29 


1 


32 


• • . 


30 


1 


28 


Y 


... 1 


1 
1 


94 




2 


20 


■„• ■ 


3 


1 


16 


• • • 


4 


1 


12 


• • • 


5 


1 


8 


• • • 


6 


1 


4 


• • • 


7 


1 


— 


• • ■ 


8 


12 


56 


• • • 


9 


12 


52 


♦ •' • 


10 


12 


48 


• • • 


11 


12 


44 







H. 


M. 


AY 




12 


40 


• • • 


13 


12 


30 


• • • 


14 


12 


32 


. . . 


15 


12 


28 


• • • 


16 


12 


24 


• • * 


17 


12 


20 


■ • • 


18 


12 


16 


• • • 


19 


12 


12 


• • • 


20 


12 


8 


• • • 


21 


12 


4 


• • • 


22 


12 




. . • 


23 


11 


56 


• • • 


24 


11 


52 


• m • 


25 


11 


48 


• • • 


26 


11 


44 


. . • 


27 


11 


40 


• • • 


28 


11 


36 


. • • 


29 


11 


32 


■ ■•"• 


30 


11 


28 


• • « 


31 


11 


24 


FNE 


1 


11 


20 


• • . 


2 


11 


16 


• • • 


S 


11 


12 


. . . 


4 


11 


8 







H. 


M. 


JNE... 




11 


4 


• • • • 


6 


11 


— 


• • • • 


7 


10 


56 


• • • • 


8 


10 


52 


• • • • 


9 


10 


48 


• • • • 


10 


10 


44 


> • • • 


11 


10 


40 


• • • • 


12 


10 


36 


• ■ • • 


13 


10 


32 


• •-• • 


14 


10 


28 


• • * • 


15 


10 


24 


• • • • 


16 


10 


20 


• • • • 


17 


10 


16 


• «. • 


18 


10 


12 


• • • • 


19 


10 


8 


• • • • 


20 


10 


4 


• • • • 


21 


10 


— 


• • • • 


22 


9 


56 


• ■ • • 


23 


9 


52 


• . . • 


24 


9 


48 


• • • • 


25 


9 


44 


• • • • 


26 


9 


40 


• • • « 


27 


9 


36 


• • • • 


28 


9 


32 



JUNE. 
JULY. 



29 

30 

. 1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 



9 
9 



31. 

28 
24 



9 


20 


9 


16 


9 


12 


9 


8 


9 


4 


9 


— 


8 


50 


8 


52 


8 


48 


8 


44 


8 


40 


8 


36 


8 


32 


8 


28 


8 


24 


8 


20 


8 


16 


8 


12 


8 


8 


8 


4 



8 — 



*.\ 



SI 



saa 



v?\ow 



s^SP^S^ 



BSE 






jJ^SS^e 






I* 



vac 



ir % 



^s, ■,( 



m^_ 



APKlL 



X 0S 




^-efl: / 



mm 



\/ ^^Ji 



V^S^J 







mm&$*^¥&hifc 



GWtj 



w-r^ 



^\ -- -<-W\T%\ Vs 






» 



• '£ TT^T^I / PC ^AJ*.-/' er>\/7 \fid-A \ // >7 '«/'// /' ^-5HP\-it\ ^"^ / V 



i .. i\A ill ~-os*\// 






* ^;- 






/ &*¥/' 



z&k^r^^f* 









^^""3 /v^" v ^ 



:1_ ^obpidS, A 



^tFf»/i 



« - - \ -Z- 



v Jgo 3. _?-=>■• --*• 









'STARS VISIBLE 



5 of-t>/-L& iC 1 



68 



ILLUSTRATED ASTRONOMY. 



TO FIND THE MAGNITUDES OF THE PLANETS, 



The magnitudes of all globes or spheres, are in proportion to one 
another, as the cubes of their diameters : — hence, if we cube the diam- 
eters of any two globes, and divide the greater product by the less, the 
quotient will show how many times the one is greater than the other. 

[Note. — The cube of any number is the number multiplied into 
itself, and that product multiplied by the first number.] 

Example. — Suppose two globes, one of 5 feet, and the other 10 
feet in diameter — 

5 10 

5 10 



25 
5 



100 
10 



125. cube of 5. 1000 cube of 10. 



Then 125 + 1000 
1000 



Hence it will be seen that the globe of 10 feet in diameter, is 8 times 
the magnitude of the less. 

To find the magnitudes of the planets, compared with that of the 
earth, observe the following Rule. — 

Cube the diameter of the earth, which is 7,912 miles, and also the 
diameter of each planet, — then if the cube of the earth's diameter, is 
greater than that of the planet, divide the greater by the less, and the 
quotient will show how many times the earth is greater than the planet; 
but if th,e cube of the diameter of any planet, is greater than the cube 
of the earth's diameter, divide the cube of the planet's diameter by the 
cube of the earth's diameter, and the quotient will show how many 
times the planet is greater than the earth. 

EXAMPLE I. 

Earth's Diameter, 7,912X7,912=62,599,744X7,912=495,289,174,- 
528, cube of earth's diameter. 

Mercury's Diameter, 3,200X3,200=10,240,000X3,200=32,768,000- 
000, cube of Mercury's diameter. 

Divide the greater by the less, — 

32,768,000,000)195.289,174 528(15 times less than the earth. 
32,768,000,000 



167,609.174,528 
163,840,000,000 

3,769,174,528 



EXAMPLE n. 

Diameter of the Sun — 

886,952X886,952X886,952=697,750,814,394,833,408. 

Divide by cube of earth's diameter — 

495,289,174,528)697,750,814,394,833,408(=1,408,734. 



Diameters. 



Cubes of their Diameters. 



Mercury, 3,200 miles 32,768.000,000 miles 

Venus, 7,700 

Earth, 7,912 

Mars, 4,189 

Vesta* 270 

Juno,* 1.400 

Ceres,* 1,600 

Pallas,* 2,100 

Moon, ..2,180 

Jupiter, 87.000 

Saturn, 79.000 

Herschel, 35,000 

Leverrier, 35,000 

Sun, 886,952 



.456,533,000,000 

" 495,289,174,528 

" 73,507,403,269 

" 19,683,000 

" 2,744,000,000 

" 4,096,000,000 

" 9.261,000,000 

" 1 0,360,232,000 

" 658,503,000,000,000 

" 493,039,000,000,000 

" 42,875,000,000,000 

" 42,875,000,000,000 

" 697,750,814,394,833,408 



m 



u 
(I 

M 

i. 
U 



* Diameters of the other Asteroids are not known. 



32,768,000,000 
456,533,000,000 
73,507,403,269) 
19.683,000( 
2,744,000.000^ 
4,096,000,000) 
9,261,000,000 
10,360,232,000- 



i 



EXAMPLE I. 

15 Mercury, 
9 Venus, j% - - 
6.73 Mars, \ nearly, 

Cube of earth's diameter, ,'25,163 Vesta, 5 7rri ro - 

495,289,174,528. ^ 180. Juno, r i, - - 
120. Ceres, ^s - - 
53 Pallas, j\ - - 
58 Moon, jV nearly, 



1 



EXAMPLE n. 



> o ~- 

i — ' -re 



3 



658,503.000,000.000. 1 1329+ Jupiter larger than the earth. 
493.039.000.000,000. | 995+Saturn " " " 

42,875,000,000.000. )> 86+ Herschel " " " 



42,875,000,000,000. 
I 697,750,814,394,833,408. 



86+Leverrier," 
1,408.734. Sun " 



Note. — The teacher might require the more advanced pupils in the class to 
work out the above problems on their slates. It would be a profitable exercise for 
them in arithmetic, as well as fixing in the mind the magnitudes of the planets. 



TO FIND THE DISTANCES OF THE PLANETS FROM THE SUN. 



The celebrated astronomer, Kepler, discovered that all the planets 
are subject to one general law, which is, that the " squares of their 
periodic times are proportional to the cubes of their mean distances 
from the sun." This law was fully demonstrated and established by 
Sir Isaac Newton. Astronomers found it very easy to ascertain the 
peritSHic times of the planets, which only required them to observe the 
time it took each planet to revolve around the sun from any particular 
star to the same star again ; but to find the distances of the planets 
from the sun, they found a much more difficult" task. By observations 
made upon the transits of Venus, the earth's distance from the Sun, has 
been found to be about 95,000,000 of miles, — hence, if we have the- pe- 
riodic times of the planets, and the distance of one of them from the 
sur <ve can, by this law of Kepler's, find the distances of the other 
pianets by the simple kule of proportion. Therefore, to find the dis- 
tance of Mercury from the sun, we say, as the square of 365 days 
(which is 133,225) is to the cube of 95,000,000 of miles, (which is 
'857,375,000,000,000,000,000,000) so is the square of 88 days, (which 



is 7,744) to a fourth term, which is the cube of Mercury's distance 
from the sun. And if the cube root of this term be extracted, the 
answer will be 37,000,000 of miles, nearly. 



THE FOLLOWING ARE THE STATEMENTS TO FIND THE DISTANCES OF 

THE OTHER PLANETS FROM THE SUN. 
As 133,225 is to 857,375,000,000,000,000,000,000 g j s the square of the per iodic 

time, in days, of each planet 

separately to the fourth term, 

. . . which will be the cube of the 

distance of the planet from 

the sun. Extract the cube 

root of the fourth term, so 

found, and it will give the 

•••■ planet's mean distance from 

the sun. 



— 



I L L DSTRATED AS T RONO M Y . 



GO 



PRINCIPAL CONSTELLATIONS VISIBLE, FROM JULY 11 TO OCTOBER 31. 



Cygnus, the Swan. — This constellation is situated a little to the 
vest of the zenith. It is represented with outspread wings, flying in 
the direction of the milky way to the southwest. The five principal 
stars are so arranged as to form a large and regular Cross. Deneb, a 
star of the first magnitude, is in the head of the Cross, and Albireo, 
situated in the beak of the Swan, forms the foot. Over the right wing 
of the Swan is a remarkable double star, known by the name of "61 
Cygni," These stars are of the 5th and 6th magnitude ; they revolve 
round a common centre of gravity between the two, in 540 years. 
These two stars will ever be memorable as being the first whose dis- 
tance from us was measured with much precision, and are the nearest 
to us, with a single exception, of any as yet known. The star (a) Cen- 
tauri is about one-third the distance of 61 Cygni. Observations have 
been made on a great many others ; but their parallax is much less, 
and in most cases is so small as not to be perceptible with the most 
accurate instruments. The distance of 61 Cygni was ascertained by 
Bessel, from his observations, in the years 1837, 1838 and 1839. He 
found their distance 592,000 times the earth's mean distance from the 
sun. So great is this distance, that a cannon ball, moving 500 miles 
an hour, would not reach those two stars in less than thirteen millions 
of years. The sun, seen from these stars, would appear like a star of 
the oth magnitude. Previous to this discovery the stars were consider- 
ed to be about the same in magnitude, and the brightest stars to owe 
their brilliancy to their being nearer to us ; but the brightest star in the 
whole heavens (Sirius, the great Dog Star,) is at a much greater dis- 
tance than these, and owes its brilliancy to its superior magnitude or 
much greater brilliancy. 

Lyra, the Harp. — This constellation is next to the Swan. For 
a description of this constellation, see explanations to Map No. 2, from 
April 18 to July 31. 

Cepheus, the King. — This constellation may be known by three 
stars of the third magnitude in a right line — in the neck, breast, 
and knee. He stands with his left foot over the pole. He holds a 
sceptre in his hand, extended towards Cassiopeia, his wife. Cepheus 
was the king of Ethiopia : the name of his queen was Cassiopeia. He 
was one of the Argonauts who accompanied Jason in his expedition 
from Greece to Colchis, in quest of the Golden Fleece, and at his death 
was changed into a constellation. 

Cassiopeia, the Lady in her Chair. — This constellation is 
situated east of Cepheus. She is represented in regal state, seated on 
a throne or chair, holding in her left hand the branch of a palm tree. 
She is surrounded by her royal famity — Cepheus, her husband, on her 
r.ght hand ; Perseus, her son-in-law, on her left, and Andromeda, her 
daughter, just above her. This constellation contains 55 stars, that are 
visible to the naked eye : five of these are of the 3d magnitude, which, 
with two smaller ones, form a figure resembling an inverted chair. 

Cassiopeia was the wife of Cepheus, king of Ethiopia. She was 
possessed of great beauty, and boasted herself fairer than Juno, the sis- 
ter of Jupiter, or the Nereides, a name given to the sea nymphs. This 
provoked the nymphs of the sea, who complained to Neptune, of the 
insult. He sent a frightful monster to punish her insolence. It was 
finally ordained that she should chain her daughter Andromeda, whom 
she tenderly loved, to a desert rock on the beach, and leave her expo- 
sed to the fury of this monster. She was thus left, and the monster 
approached ; but as he was going to devour her, Perseus killed him. 

Andromeda. — This constellation is south of Cassiopeia. It con- 
tains 66 stars, three of which are of the third magnitude, viz : Sirrah, 
in the head ; Mirach, in the breast, and Almak, in the feet. They 
stand nearly in a straight line. Andromeda, the daughter of Cepheus 
and Cassiopeia, was exposed to be devoured by a Sea Monster, to 
appease the wrath of Neptune. She was accordingly chained to a rock 
neai Jofpa, (now Jaffa in Syria,) and at the moment the monster was 
going to devour her, Perseus, who was returning through the air from 
the conquest of the Gorgons, saw her and was captivated by her 
beauty. He promised to deliver her and destroy the monster, if her 
father would give her to him in marriage. Cepheus consented, and 



Perseus instantly changed the sea monster into a rock, by showing him 
Medusa's head, which was still reeking in his hand. This fable of 
Andromeda and the sea monster might mean that she was courted by 
some monster of a sea captain, who attempted to carry her away, but 
was prevented by another more gallant and successful rival. 

Pegasus, the Flying Horse. — This constellation is represented 
with wings. It may be known by four stars, which form a regular 
quadrangle or trapezium. The northeastern of these four stars is in the 
head of Andromeda. Their names are (a) Markab, ((?) Scheat, Alge- 
nib, and («) Sirrah, in the head of Andromeda. According to fable, 
Pegasus was a winged horse, which sprang from the biood of Medusa, 
when Perseus cut off her head. 

Equuleus, the Little Horse. — This is a small cluster, of stars 
west of the head of the Flying Horse. Only the head is visible. This 
is supposed to represent the horse which Mercury gave to Castor, and 
which he named Celeris. 

Delphinus, the Dolphin. — This is a beautiful little constella- 
tion, between the Eagle and Equuleus, or Little Horse. It may be dis- 
tinguished by four stars in the shape of a diamond, with two small stars 
which form the tail. (See map No. 2, and explanation.) 

Sagittarius, the Archer. — This is the tenth constellation in 
the zodiac. It is situated to the southwest, near the horizon. It may 
be known by five stars, forming a figure resembling a short handled 
dipper. It appears turned up, with the handle to the north, and the 
bowl towards the east. Sagittarius, or Chiron, the son of Saturn, 
was a twofold being — half man and half horse. This constellation was 
intended, no doubt, by the ancients to represent the season for hunt- 
ing ; for when the sun enters this sign, the trees have cast their foliage, 
which enables the hunter to pursue his game to better advantage. 

Capricornus, the Goat. — This is the next sign in the ecliptic, 
east of Sagittarius. There are two conspicuous stars in the head, 
called Giedi and Dabih. Giedi is the most northern star of the two, 
and is double. Several other stars may be traced out by reference to 
the map. The goat was observed by the ancients to be fond of climb 
ing high mountains and lofty precipices, and was therefore considered 
emblematical of the sun, which, having in this sign reached his great- 
est southern declination, begins to re-ascend towards the north. 

Aquarius, the Water Bearer. — This constellation is repre- 
sented by the figure of a man pouring out water from an urn, aad is 
north and east of Capricornus. It may easily be traced by reference to 
the map. The ancient Egyptians supposed the disappearing of Aqua- 
rius caused the waters of the Nile to rise by the sinking of uis urn in 
the water. 

Pisces, the Fishes. — This is the last sign in the zodiac. This 
constellation is represented by two fishes, a considerable distance apart, 
tied by a cord or riband. The stars in this constellation are of the 
4th and inferior magnitudes. The probable origin of this sign was 
from the fact, that when the sun was in it, it was the season when fish 
were abundant, and easily taken. 

Piscis, the Southern Fish. — This constellation is south of 
Aquarius, and is easily distinguished by the star Fomalhaut, of the first 
magnitude, with two small stars, which form an equilateral triangle. 
These three are the only important stars in this constellation. This 
constellation is supposed to have taken its name from the transformation 
of Venus into the shape of a fish, when she fled, terrified at the horrible 
advances of the monster Typhon, who was said to have an hundred 
heads. 

Ursa Major, the Great Bear. — This constellation is directly 
north, and touches the horizon. The Dipper, which is a part of this 
constellation, is a little to the northwest of the north star, and is right 
side up, with the handle to the west. (For explanation, see map No. 1.) 

Lacerta, the Lizard. — This is a small constellation near the 
zenith. It contains a few stars of inferior magnitude. 

I 



ILLUSTRATED ASTRONOMY 



MAP, FROM JULY n TO OCTOBER 31. 

[ ijp 3 The Stars and Constellations upon this Map will occupy the exact positions in the heavens as they are laid down 
on the Map, at the times for observations, as specified in the table. The centre of the Map represents the zenith of New- 
York, or any place situated upon the parallel of latitude of 41° north. There will be only six stars of the first magnitude 
visible, the most conspicuous of which will be Deneb, Vega, Altair, and Capella. The other two, Aldebaran and Fomalhaut, 
being near the horizon, may not be visible unless the atmosphere is very clear.] 



STARS OF THE FIRST MAGNITUDE. 



NAMES OF THE CONSTELLATION'S AND PRINCIPAL STARS. 

CYGNUS, The Swan — (Deneb the principal star.) — This 
star is situated directly west, and about 20° from the zenith. It is in 
the middle of .the Milky-way. 

LYRA., The Harp — (Vega.) — This star is about 20° west of 
Deneb. 

AQIIILA, The Eagle — (Altair.) — This star is situated towards 
the southwest, and about 35° from the zenith. 



PISCIS, Southern Fish — (Fomalhaut.) — This star is about 
10° east of south, and about 15° above the southern horizon — perhaps 
it will not be visible only when the atmosphere is clear. 

TAURUS, The Bull — (Aldebaran.) — This star is nearly north- 
east, and within 10° of the horizon. It will not be visible only when 
the atmosphere is very clear. 

AURIGA, The Charioteer — (Capella.) — This star is directly 
east of the North Star, and about midway to the horizon. 



TABLE OF THE TIMES FOR OBSERVATIONS. 

SHOWING THE DAY AND HOUR OF THE NIGHT WHEN THE STARS OCCUPY THE POSITIONS INDICATED ON THE MAP. 



JULY 



AUGUST.. 





H. 


M. 


22 


1 


56 


23 


1 


52 


24 


1 


48 


25 


1 


44 


26 


1 


40 


27 


1 


36 


28 


1 


32 


29 


1 


28 


30 


1 


24 


31 


1 


20 


1 


1 


16 


2 


1 


12 


3 


1 


8 


4 


1 


4 


5 


1 


— 


6 


12 


56 


7 


12 


52 


8 


12 


48 


9 


12 


44 


10 


12 


40 


11 


12 


36 


12 


12 


32 


13 


12 


28 


14 


12 


24 


15 


12 


20 


16 


12 


10 







H. 


M. 






H. 


M. 


AUGUST... 


17 


12 


12 


SEPTEMBER 12 


10 


28 


• * • • 


18 


12 


8 


• • • • 


13 


10 


24 


• ■ • • 


19 


12 


4 


• • • • 


14 


10 


20 


• • • • 


20 


12 


— 


• • • • 


15 


10 


16 


• • ■ ■ 


21 


11 


56 


■ a • • 


16 


10 


12 


• • • • 


22 


11 


52 


• • • • 


17 


10 


8 


* » • • 


23 


11 


48 


• • • • 


18 


10 


4 


• • • • 


24 


11 


44 


■ • • • 


19 


10 


— 


• • • • 


25 


11 


40 


• • • • 


20 


9 


56 


• • • • 


26 


11 


36 


• • • • 


21 


9 


52 


• • • • 


27 


11 


32 


* • • • 


22 


9 


48 


• • • • 


28 


11 


28 


• • • • 


23 


9 


44 


• • • • 


29 


11 


24 


• • • • 


24 


9 


40 


• • » • 


30 


11 


20 


* • • • 


25 


9 


36 


■ • • • 


31 


11 


16 


• • ■ • 


26 


9 


32 


SEPTEMBER 1 


11 


12 


• • • • 


27 


9 


28 


• • • • 


2 


11 


8 


• • • • 


28 


9 


24 


• • • • 


3 


11 


4 


• • • • 


29 


9 


20 


• • • • 


4 


11 


— 


• • ■ • 


30 


9 


16 


• • • • 


5 


10 


56 


OCTOBER. 


.. 1 


9 


12 


• • • • 


6 


10 


52 


• • • • 


2 


9 


8 


■ ■ ■ ■ 


7 


10 


48 


• • ■ ■ 


3 


9 


4 


• • * • 


8 


10 


44 


■ • • • 


4 


9 


— 


• • • • 


9 


10 


40 


• • • • 


5 


8 


56 


• • • • 


10 


10 


36 


• • • • 


6 


8 


52 


• • • • 


11 


10 


32 


• • • • 


7 


8 


48 



n. 



31. 



rrt 


)BER... 8 


8 


44 


. . 


9 


8 


40 


. . 


10 


8 


36 


. . 


11 


8 


32 


. . 


12 


8 


28 


. . 


13 


8 


24 


. a 


14 


8 


20 


. . 


15 


8 


16 


. . 


16 


8 


12 


. . . 


17 


8 


8 


. • 4 


18 


8 


4 


■ • a 


19 


8 


— 


. . . 


20 


7 


56 


m t ■ 


21 


7 


52 


• • 1 


22 


7 


48 


• • ■ 


23 


7 


44 


. . . 


24 


7 


40 


. . . 


25 


7 


36 


. . . 


26 


7 


32 


. . . 


27 


7 


28 


. . . 


28 


7 


24 


. . . 


29 


7 


20 


. . . 


30 


7 


16 


• • a 


31 


7 


12 








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72 



ILLUSTRATED ASTRONOMY 



ZODIACAL LIGHT. 




The Zodiacal Light is a faint luminous appearance, which accom- 
panies the Sun, and is seen just after twilight in the evening, or before 
it commences in the morning. It was observed by Kepler, who sup- 
posed it to be the Sun's atmosphere, and afterwards accurately described 
by Cassini, in 1683, who gave it the name by which it is now known, 
in consequence of its always being in the Zodiac. It probably sur- 
rounds the sun on all sides ; but is shaped like a lens, or burning glass, 
the circumference of which is directly over the Sun's equator. The edge 
being always presented to us gives it the appearance of a pyramid or 
cone. There can only that portion of it be seen which remains above 
the horizon after twilight has ceased. When seen, it extends from the 
horizon upwards, and following the course or path of the Sun. For 
this reason it is scarcely visible in our latitude, as the path of the Sun 
during most of the year, is very oblique to the horizon : consequently 
it is obscured by twilight, which does not cease until the Sun is 18 
degrees below the horizon. At the equator it can be favorably observed 
most of the year, and often presents a beautiful appearance. The 
most favorable times for observing it in our latitude are in the evening, 
during the months of April and May, and in the^morning during the 
months of October and November, as the path of the sun is nearer per- 
pendicular to the horizon than at any other times during the year. It 



appears in form like a pyramid, with the base at the horizon — tapering 
to a point, and more or less inclined to the horizon. 

Its length above the horizon varies, according to circumstances, from 
40 to 100 degrees, and its breadth at the base perpendicular to its axis 
varies from 8 to 30 degrees. It is extremely faint and ill-defined in 
our climate ; but is much more conspicuous in tropical countries. An 
allusion is made to this phenomenon in a work published by J. Chil- 
drey in 1661, in the following passage : — "In the month of February, 
for several years, about six o'clock in the evening, after twilight, I saw 
a path of light tending from the twilight towards the Pleiades, as it were 
touching thern : this is to be seen whenever the weather is clear, but 
best when the moon does not shine. I believe that this phenomenon 
has been before visible, and will hereafter appear, always at the above 
mentioned period of the year ; but the cause and nature of it I cannot 
guess, and therefore leave it to the inquiry of posterity." 

Various opinions and theories have been advanced by astronomers, 
both ancient and modern ; but none have been able to settle the point 
beyond controversy. Cassini thought it might proceed from an innu- 
merable multitude of little bodies revolving around the Sun, reflecting a 
faint light, like that of the milky-way. Kepler ascribed its ap^eaiaiice 
to the atmosphere which he supposed to surround the Sun. Both of 
these theories have been discarded as being untenable. Professor 
Olmstead supposes it to be a nebulous body, or thin gaseous mass, 
revolving around the Sun, causing the Meteoric Showers that have 
occurred for several years in the month of November, in consequence 
of the earth's near approach to it, in its annual course around the Sun. 

Herschell and Professor Nichol assert that the Zodiacal Light is a 
phenomenon precisely similar to that exhibited by the nebulous stars, 
and if we were living upon some distant star, the Sun would appeal 
to us like a star surrounded by a faint light similar to that of a candle 
seen at a short distance, in a foggy or thick atmosphere. 

The present theory of the Zodiacal Light may be summed up in a 
few words — namely, that the matter of which the Sun and planets are 
composed was originally in a thin gaseous state, and has been con- 
densed into solid bodies, which form the Sun and planets ; that the 
Zodiacal Light is a portion of this matter, which has not as yet subsided 
into the Sun. It is estimated to extend beyond the orbit of Mercury, 
and perhaps that of Venus ; if so, they must pass through it twice during 
each revolution around the Sun. 



A SIMPLE METHOD TO FIND THE CIRCUMFERENCE OF THE EARTH. 



All circles, great or small, are supposed to be divided into 360 equal 
parts, called degrees. From this it will be seen that a degree has no 
definite measure ; but depends upon the magnitude of the circle. If we 
suppose a circle to be 360 miles in circumference, then one degree 
would measure just one mile ; but if the circle were greater a degree 
would be greater, and if less a degree would be less. We will now 
apply this principle of the circle to measure the circumference of the 
earth. In order to do this, we must take two places some distance 
apart and under the same meridian ; we. will suppose New York 
and Albany. 

We will suppose that the exact distance between the two places has 
been found by exact measurement to be 138ij miles — (this distance 



probably does not vary much from the truth.) We will now place an 
observer at each place with accurate instruments, and on a particular 
night, at 12 o'clock, the observer at New York finds a particular star 
exactly in his zenith, or over head ; but the observer at Albany finds 
the same star two degrees to the south of his zenith, — hence it will be 
seen that there are two degrees between the two places ; and as the 
distance, by measurement, was found to be 138^ miles, the two degrees 
between New York and Albany are equal to 138| miles, or one 
degree equals 69£ miles. Now, if we multiply the number of de- 
grees in the whole circle or circumference of the earth (360) by 
69^ miles, it will give 24,930 miles the whole circumference of 
the earth. 



ILLUSTRATED ASTRONOMY 



73 



PRINCIPAL CONSTELLATIONS VISIBLE, FROM NOVEMBER 1 TO JANUARY 20. 



Perseus, and Medusa's Head. — This constellation is directly 
in the zenith, or over head. It contains two stars of the 2d magnitude. 
The one in the breast of Perseus is called Mirzak, or Algenib; the 
other is Algol, in Medusa's head : it is about 15° east of the zenith. 
This star is remarkable on account of its changeableness. It changes 
in 4 hours from the 2d to the 4th magnitude. It remains in this condi- 
tion 18 minutes, when it begins to increase in brightness ; and in 4 
hours and 40 minutes appears again of the 2d magnitude : in which 
state it continues 61 hours, when it begins to diminish again. Dr. Her- 
schel attributes its variableness to spots upon its surface like those of 
the sun, and that it revolves upon its axis. 

[History. — Perseus was the son of Jupiter and Dan.e. He was no 
sooner born than he was cast into the sea with his mother, and was 
driven on the coast of one of the islands of Cyclades. Polydectes, 
the King of the place, treated them with kindness, and placed them 
in the care of the Priests of Minerva's Temple. He promised to pre- 
sent the King with the head of Medusa, the only one of the Gorgons 
who was subject to mortality. They were represented with serpents 
wreathing about their heads instead of hair ; their bodies grew indisso- 
lubly together, and their very looks had the power of turning into stone 
all those on whom they fixed their eyes. Being equipped by the gods, 
he mounted into the air, conducted by Minerva, and came upon the 
monsters, who, with the watchful snakes, were asleep, and with one 
blow cut off her head. Perseus then made his way through the air, 
with Medusa's head yet bleeding, in his hand, and from the blood 
which dropped from it as he flew, sprang all those innumerable ser- 
pents that have ever since infested the sandy deserts of Lybia.] 

Triangulum, the Triangle. — This is a small constellation 
southwest from Medusa's Head, in the constellation Perseus. It may 
be known by three stars, which form a triangle. This constellation is 
of recent origin. 

Aries, the Ram. — This constellation lies to the southwest, about 
30° from the zenith, and may easily be distinguished by three bright 
stars in the head of the Ram, and nearly in a right line. This constel- 
lation twenty-two centuries ago occupied the first sign in the ecliptic ; or 
at that time the constellations of the zodiac and the signs of the ecliptic 
corresponded to each other : but in consequence of the retrograde mo- 
tion of the equinoxes, 50" a year, the constellations of the zodiac and 
the signs of the ecliptic have been separated from each other, by the 
falling back of the signs in the ecliptic about 31 degrees : so that the 
constellation Aries is now in the sign Taurus of the ecliptic ; and Tau- 
rus in Gemini, and Gemini in Cancer ; and so on. This constellation 
probably received its name from the Chaldean Shepherds, who were in 
those days the best astronomers, from the fact that their occupation led 
them to be on the watch during the night, to defend their flocks from 
the ravages of wild beasts. They observed that when the sun entered 
this division of the heavens the lambs were with their flocks, or that it 
was the season for the increase of their flocks — hence the Ram was 
very appropriately made to represent this sign. 

Taurus, the Bull. — This constellation is south, about 30° from 
the zenith, and will be easily distinguished by the star Aldebaran, of 
the first magnitude, situated in the Bull's eye. There are two very 
important clusters in this constellation, the Hyades on the head, and 
the Pleiades on the neck of the Bull. This constellation probably 
derived its name, as well as the other signs of the zodiac, from some 
particular phenomenon which was apparent at that particular time. It 



was intended to show that this was the season for the increase of the 
ox species — hence the name Taurus, or Bull. 

Gemini, the Twins. — This constellation is situated a little to the 
south of east, and. may be known by two stars of the 2d magnitude, one 
in each head of the Twins — their names («) Castor and (@) Pollux. 
This sign was originally represented by two goats, and was probably 
intended to indicate the season for the multiplication of this animal, as 
well as ti, show that there were usually two at a birth. 

Cancer, the Crab. — This constellation is next east of Gemini. 
It contains stars only of the 4th magnitude. It was observed by the 
Ancients, that the sun, when it enters Cancer, passes sideway along 
the tropic, without crossing it, which was fitly represented by a crab, 
which moves sideways. 

Orion. — This constellation is southeast of Taurus, and is one of the 
most conspicuous constellations in the heavens. It contains two stars 
of the first magnitude. (Note. — See description of Map No. 1.) 

Canis Minor, the Little Dog. — This constellation is south- 
east of Gemini. It contains one star of the first magnitude, Procyon, 
and one of the 3d, Mirza, in the head of the Dog. 

Canis Major, the Great Dog. — This constellation is situated 
to the southeast, and near the horizon. The principal star is Sirius, 
the brightest star in the whole heavens. (Note. — See explanation to 
Map No. 1.) 

Lepus, the Hare.— This constellation is south of Orion. It con- 
tains three stars of the 3d magnitude. It is situated west of the Geeat 
Dog, which seems to be pursuing it from east to west, owing to the 
motion of the earth on its axis. The hare is one of those animals 
which Orion delighted in hunting, and for this reason was made into a 
constellation, and placed near him, among the stars. 

Eridanus, the River Po.— This constellation occupies a largo 
space in the heavens directly south of Taurus. It will be found diffi- 
cult to trace it, in all its windings. Its entire height is 130 degrees. 
It commences near the star Rigel, in the foot of Orion. Eridanus is 
the name of a celebrated river in Italy, now known by the name of the 
river Po. 

Cetus, the Whale. — This constellation occupies the largest 
space of any in the heavens, and is west of the River Po. As the 
whale is the chief monster of the ocean, so is it the largest constella- 
tion in the heavens. It is considered to be the famous sea monster 
sent by Neptune to devour Andromeda, because her mother, Cassio- 
peia had boasted herself fairer than Juno, or the sea nymphs — but was 
slain by Perseus, and placed among the stars, in honor of his heroic 
deeds. 

Monoceros, the Unicorn. — This constellation is east of Orion, 
and was made out of the unformed stars of the ancients, which lay scat- 
tered over a large space between the two dogs Canis Major and Canis 
Minor. The Monoceros is a species of Unicorn or Rhinoceros. It is 
about the size of a horse, with one horn growing out of the middle of 
its forehead. 

Columba, the Dove. — This constellation is south of the Lepus, 
The Hare. It is so near the horizon that it probably will not be 
visible. It was introduced among the constellations by Rogu in 1679. 

Camelopardalus, the Giraffe. — This constellation was formed 
by Hevelius, in the beginning of the 17th century. It was made up 
of stars not included in the adjacent constellations, viz: Perseus, Au- 
riga, the head of Ursa Major, and the Pole Star. 



1 

74 ILLUSTRATED ASTRONOMY. 

j 


MAP, FROM NOVEMBER 1 TO JANUARY 20. 


T IST 1' HE Stars and Constellations upon this Map will occupy the exact positions in the heavens as they are laid down j 


on the Map, at the times for observations, as specified in the table. The centre of the Map represents the zenith of New- York, 


or any place situated upon the parallel of latitude of 41° north. There will be nine stars of the first magnitude above the hori- 


zon. The star Vega, in the Harp, being so near the northern horizon, may not be visible. There will be several of the most 


conspicuous constellations in the whole heavens visible, as well as a considerable number of stars of the first magnitude. The 


principal constellations are Auriga, Taurus, Orion, Canis Major, and Canis Minor. This is the best season for observa- 


tion during the year, as the atmosphere is generally more clear than at any other time, and the stars twinkle with a beautiful 


brilliancy.] 


STARS OF THE FIRST MAGNITUDE. 


names of the constellations and principal stars. 


ORION, Orion — (Betelgeuse.) — This star is in the right shoul- 


AURIGA, The Charioteer — (Capslla the principal star.) — 


der of Orion, and situated southeast about 35 degrees. 


This star is about 15° northeast of the zenith. 


" (Rigel.) — This star is on the left foet of Orion, southeast from 


TAURUS, The Bull— (Aldebaran.)— This star is in the Bull's 
Eye, and is situated about 25° south of the zenith, and 5° east of the 
meridian. 

CYGNUS, Thk Swan— (Deneb.)— This star is situated iri the 
Milky Way, and west of the North Star, about midway to the horizon. 


Betelgeuse. 

CANIS MAJOR, Great Dog— (Sirius.)— This star is situated 
southeast, about 20 degrees above the horizon. 

CANIS MINOR, Little Dog — (Procyon.)— This star is south- 
east, and about 40 degrees above the horizon. It is nearly north of 
Sirius. 


LYRA, The Harp — (Vega.) — This star is northwest of the North 


LEO MAJOR, Great Lion — (RegulllS.) — This star is nearly 


Star and close to the horizon — probably not visible. east, and about 15° above the horizon. 


TABLE OF THE TIMES FOR OBSERVATIONS. 


SHOWING THE DAY AND HOUR OF THE NIGHT WHEN THE STARS OCCUPY THE POSITIONS INDICATED ON THE MAP. 


h. m. 


h. at. 


H. M. 


H. M 


NOVEMBER.. 1 1 28 


NOVEMBER 24 11 56 


DECEMBER 17 10 24 


JANUARY... 9 3 56 


2 1 24 


25 11 52 


18 10 20 


10 8 52 




3 1 20 


26 11 48 


19 10 16 






11 8 43 




4 1 16 


27 11 44 


20 10 12 






12 8 44 


■ 


5 1 12 


28 11 40 


.... 21 10 8 






13 8 40 




6 18 


29 11 36 


..... 22 10 4 






14 8 36 




... 7 14 


30 11 32 


23 10 — 






15 8 32 




8 1 — 


DECEMBER 1 11 28 


24 9. 56 






16 8 28 




9 12 56 


2 11 24 


25 9 52 






17 8 24 


. 


10 12 52 


.... 3 11 20 


26 9 48 






18 8 20 


f ■ 


11 12 48 


4 11 16 


27 9 44 






±9 8 16 


. 


12 12. 44 


5 11 12 


28 9 40 






20 8 12 


i 


... v 13 12 40 


6 11 8 


29 9 36 






21 8 8 




. .. 14 12 36 


7 11 4 


30 9 32 






22 8 4 




15 12 32 


.... 8 11 — 


31 9 28 






23 8 — i 




16 12 28 


9 10 56 


JANUARY... 1 9 28 






24 7 56 




17 12 24 


10 10 52 


2 9 24 






25 7 52 




.18 12 20 


.... 11 10 48 


3 9 20 






26 7 48 




.... 19 12 16 


12 10 44 


4 9 16 






27 7 44 




. ... 20 12 12 


13 10 40 


5 9 12 






28 7 40 




21 12 8 


.... 14 10 36 


.... 6 9 8- 






29 7 36 




22 12 4 


.... 15 10. 32 


7 9 4 






30 7 32 


f 
1 


23 12 — 


16 10 28 1 


.... 8 9 — 






31 7 28 - 



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76 



ILLUSTRATED ASTRONOMY 



PROBLEMS PERFORMED WITH THE TERRESTRIAL GLOBE. 



Problem 1. — To find the Latitude of any given place. 

Rule. — Bring the given place to the graduated side of the brass 
meridian, and the degree on the brass meridian over the place is the 
latitude, which is either north or south. 

Q. What is the latitude of New York ? 

A. About 41 degrees north. 

Q. What places have no latitude? 

A. All places on the equator. 

Q. Find the latitude of the following places : — 
London, Philadelphia, Boston, Washington, 

Edinburgh, Rome, Dublin, Amsterdam, 

Moscow, Stockholm, Quito, Mexico, 

Algiers, Astoria, Cape of Good Hope, Halifax, 

Norfolk, Aleppo, Athens, Ispahan, 

Madras, Madrid, Cape Horn, Cairo, 

Prague, Dantzic, Teneriffe, Lisbon, 

Tripoli, Paris, Lima, Vienna. 

Problem 2. — To find the Longitude of any given place. 

Rule Bring the given place to the brass meridian, and the degren 

on the equator under the brass meridian, is the longitude. (Note. — Lon- 
gitude is reckoned from the meridian of Greenwich, 180 degrees east 
and west.) 

Q. What is the longitude of New York ? 

A. 74 degrees west. 

Q. What is the longitude of Pekin? 

A. 116 degrees east. 

Q. Find the longitude of the following places : — 
Washington, Hartford, Sandwich Islands, Gibraltar, 

Quebec, Rhodes, Calcutta, Constantinople, 

Canton, Havana, Jerusalem, Nankin, 

Pekin, St. Petersburgh, Venice, Berlin, 

Astoria, Cape Horn, New Orleans, Rio Janeiro. 

Problem 3. — To find any place whose latitude and longitude are 
given. 

Rule. — Bring the given longitude to the brass meridian, and under 
the given latitude is the place required. 

Q. What place is situated in seventy-four degrees west longitude, 
and 41 north latitude ? 

A. New York. 

Q. What places have the following latitudes and longitudes ? 

Lat. 42° north, Lon. 71° west. Lat. 34° south, Lon. 18° east. 

Lat. 53° north, Lon. 6° west. Lat. 41° north, Lon. 72° west. 

Lai. 38° north, Lon. 9° west. Lat. 39° north, Lon. 75° west. 

Lat. 46° north, Lon. 75° west. Lat. 32° north, Lon. 81° west. 

Problem 4. — To find all those places that are in the same latitude 
or longitude as a given place. 

Rule. — Bring the given place to the brass meridian ; then all the 
places under the meridian have the same longitude ; turn the globe 
round, and all places which pass under the latitude of the place have 
the same latitude. 

Q. What places have nearly the same longitude as New York ? 

A. Albany, Montreal, Bogota. 

Q. What places are in the same latitude ? 

A. Boston, Madrid, Naples, Constantinople. 

Q. What places have the same longitude and latitude as the follow- 
ing places : — 

Washington, London, St. Petersburgh, Rome, Cairo, 

New Orleans, Mexico, . Canton, Calcutta, Dublin ? 

Problem 5.— To find the difference of Latitude between any two 
places. 

Rule. — Find th« latitude of each place, and note them down ; then 
if both places are on the same side of the equator, subtract the less 
latitude from the greater: if they are on the opposite sides of the 
equator, add the latitudes. 

Q. What is the difference of latitude between New York and London ? 

A. New York 41° north, London 51° north ; difference 10° 



Q. What is the difference of latitude between Washington and Cape 
Horn? 

A. Washington 37° north, Cape Horn, 56° south. — Sum 93.° 

Q. Find the difference of latitude between the following places : — 

New Orleans and Quebec. Mexico and Rio Janeiro, 

Madrid and Cairo, Pekin and Botany Bay, 

St. Petersburgh and Rome, Cape of Good Hope and Cape Horn. 

Problem 6. — To find the difference of longitude between any two 
places. 

Rule. — Find the longitude of each place, and note them down : then, 
if both places are east or west of the meridian, subtract the less lon- 
gitude from the greater ; but if one is east and the other west add tho 
longitudes. 

Q. What is the difference of longitude between New York and New 
Orleans ? 

A. New York 74°; New Oneans 90°, west — difference 16 degrees. 

Q. What is the difference in longitude between Boston and Rome ? 

A. Boston 71° west ; Rome 12° east — sum, 83 degrees. 

If the sum of the longitudes exceed 180 degrees, subtract it from 360 
degrees ; the remainder will be the difference in longitude ; as, Astoria 
124° west; Peki.. 116° east=240 : 360—240=120° difference in 
longitude. 

Problem 7. — The hour of the day at any place being given, to find 
what o'clock it is at any other place. 

Rule. — Bring the place at which the time is given to the brass 
meridian ; set the index to the given hour, then turn the globe till the 
proposed place comes to the meridian; the index will point to the hour 
required. If the place required is east of the given place, it is later; 
if to the west, it is earlier. 

Q. When it is noon at New York, what is the time in London ? 

A. 4 o'clock 56 min. 

Q. When it is noon at Washington, what is the hour at 
New Orleans, Mexico, Quebec, Boston, Astoria, Pekin, 

Cape Horn, Rome, St. Petersburgh, Moscow, Canton, Dublin ? 
When it is midnight at New York, what is the hour at 
Paris, Cairo, Calcutta, St. Helena, Gibraltar, Havana, 

Constantinople, Mexico, Astoria, Nankin, Tunis, Cadiz ? 

Problem 8. — The hour of the day being given at any place, to find 
all places on the globe where it is then noon, or any other given hour. 

Rule. — Bring the place to the brass meridian ; set the index to the 
hour of that place ; turn the globe till the index points to the other 
given hour ; then all places under the brass meridian will be the places 
required. 

Problem 9. — To find the Antaeci of any place. 

Rule. — Bring the place to the brass meridian, and find its latitude , 
then, under the same degree of latitude, on the opposite side of the 
equator will be the Antceci. 

Problem 10. — To find the Periceci of any place. 

Rule. — Bring the given place to the brass meridian, and set the 
index to twelve ; turn the globe till the index points to the other twelve, 
and under the same degree of latitude will be the Periceci. 

Problem 11. — To find the Antipodes of any place. 

Rule. — Bring the place to the brsss meridian, and find its latitude , 
set the index to twelve, and turn the globe till the index points to the 
other twelve ; then under the same degree of latitude, on the other side 
of the equator, will be the antipodes. 

Problem 12. — To find the distance in miles between any two places 
on the globe. 

Rule. — Lay the quadrant of altitude over the two places, so that the 
division marked will be on one of the places, and it will show the 
number of degrees between them ; which, multiplied by 69^ will give 
the distance in miles. 

Problem 13. — To find the Sun\$ Longitude or place in the Ecliptic, 
and his declination, in any given month or day. 



ILLUSTRATED ASTRONOMY. 



77 



Rule. — Look for the given day in the circle of months on the wooden 
horizon, and opposite to it, in the circle of signs, are the sign and 
degree in which the sun is for that day. Find the same sign and 
degree in the ecliptic on the surface of the globe ; bring the degree of 
the ecliptic, thus found, to the brass meridian, and the degree of the 
meridian will be the declination. 

Problem 14. — To find the time at which the Sun rises and sets at any 
place, the day in the year, and the length of the day and night at that 
place. 

Rule. — Raise the pole (of the hemisphere in which the place is sit- 
uated) as many degrees above the horizon as are equal to the latitude 
of the place; bring the sun's place on the given day, to the meridian, 
and set the index to 12 : bring the sun's place to the eastern horizon, 
and the index will show the time of the sun's rising ; bring the sun's 
place to the western edge of the horizon, and the index will show the 
hour of setting. Double the time of the sun's setting, and the length of 
the day will be had ; double the time of the sun's rising, and the length 
of the night will be had. 

Problem 15. — To find the length of the longest and shortest days and 
nights at any place on the earth. 

Rule. — If the place is in the northern hemisphere, elevate the north 



pole till the horizon cuts the brass meridian in the degree correspond- 
ing to the latitude of the place ; bring the first degree of Cancer to the 
meridian, and set the index to 12 ; find the sun's place in the ecliptic, 
(by problem 13,) and bring it to the eastern edge of the horizon, and 
the index will show the hour of the sun's rising ; double this time, and 
it will give the length of the longest night. Bring the sun's place to 
the western edge of the horizon, and the index will show the hour of 
setting ; double this time, and you will have the length of the longest 
day at that place. If the place is in the southern hemisphere, elevate 
the south pole to correspond with the latitude of the place ; bring the 
first degree of Capricorn to the meridian, and proceed as above. 

Q. What is the length of the longest day and shortest night at New 
York? 

A. Longest day, 14 h. 56 min. ; shortest night, 9 h. 4 min. 

Problem 16. — To find those places where the Sun does not rise or set 
on a given day. 

Rule. — Find the sun's declination on the given day, (by prob. 13,) 
raise the pole (nearest to the sun's place,) as many degrees above the 
horizon as are equal to the declination ; turn the globe round on its 
axis, and at all places that do not come above the horizon the sun does 
not rise on that day ; and at all places around the other pole that do 
not pass below the horizon, the sun does not set on that day. 



PROBLEMS PERFORMED WITH THE CELESTIAL GLOBE, 



[Latitude, on the Celestial Globe, is reckoned 90°, either north 
or south, on circles of Celestial Latitude, which are at right angles to 
the ecliptic. (See Diagram, page 55.) 

Longitude, on the Celestial Globe, is reckoned on the ecliptic, 
from the first degree of Aries, eastward, round the globe. 

Declination, is reckoned from the equinoctial, either north or 
south. 

Right Ascension, is reckoned on the equinoctial, from the first 
degree in Aries, eastward, round the globe.] 

Problem 1. — To find the Right Ascension and Declination of the 
Sun or a Star. 

Rule. — Bring the sun or star to that part of the brass meridian 
which is numbered from the equinoctial towards the poles : the degree 
on the brass meridian, over the place, will show the declination ; and 
the number of degrees on the equinoctial, between the brass meridian 
and the first point of Aries, is the right ascension. 

Required — the right ascension and declination of the following stars: 



Aldebaran, in Taurus, 
Sirius, in the Great Dog, 
Vega, in the Harp, 



Arcturus, in Bootes, 
Capella, in Auriga, 
Regulus, in Leo. 



Problem 2. — To find the Latitude and Longitude of a Star. 

Rule. — Place the end of the quadrant of altitude, which is marked 
90°, on the north or south pole of the ecliptic, according as the star is 
north or south of the ecliptic ; then move the other end till the gradua- 
ted edge of the quadrant comes to the star. The number of degrees on 
the quadrant, between the ecliptic and the star, is the latitude ; and the 
number of degrees on the ecliptic, reckoned eastward, from the first 
point of Aries to the quadrant, is the longitude. 

Example. — Required, the latitudes and longitudes of the following 
stars : — 

Aldebaran in Taurus. Ans. Latitude 5° 28' S. ; longitude, 2 signs 
6° 53', or 6° 53' in Gemini. 



Deneb, in the Swan, 
Antares, in Scorpio, 
Fomalhaut, in the S. Fish, 



Altair, in the Eagle, 
Rigel, in Orion, 
Pollux, in Gemini. 



the 



Problem 3. — The declination and right ascension of a Star_ 
Moon, a Planet, or a Comet, being given, to find its place on the globe. 

Rule — Bring the given degrees of right ascension to that part of 
the brass meridian which is numbered from the equinoctial towards the 
poles ; then under the given declination on the brass meridian you will 
find the star or planet. 



Q. What stars have the following right ascensions and declinations ? 

Right Ascension. Declination. Right Ascension. Declination 

76° 14' 8° 27' S. 86° 13' 44° 55' N 

83 6 34 11 S. 99 5 16 26 S. 

25 54 . 19 50 N. 11 11 59 38 N. 

53 54 23 29 N. 46 32 9 34 S. 

Problem 4. — The latitude and longitude of the Moon, a Star, or a 
Planet, being given, to find its place on the globe. 

Rule. — Screw the quadrant of altitude on the pole of the ecliptic, 
and place the other end on the given degree of longitude in the ecliptic ; 
then, under the given latitude, on the graduated edge of the quadrant, 
you will find the star, or place of the moon or planet. 

Q. What stars have the following latitudes and longitudes ? 



Latitude 


s. 


Longitudes. 


Latitudes. 


Longitudes. 


16° 3' 


S. 


2 s 25° 51' 


10° 4' N. 


3 s 17° 21' 


22 52 


N. 


2 18 57 


21 6 S. 


11 56 


5 29 


S. 


2 6 53 


12 3 S. 


1 11 25 


44 20 


N. 


7 9 22 


27 N. 


4 26 57 



Problem 5. — The latitude of a place, the day and hour being given, 
to place the globe in such a manner as to represent the heavens at that 
time, in order to -point out the situations of the constellations and remark- 
able stars. 

Rule. — Elevate the pole for the latitude of the place, and set the 
globe due north and south by a meridian line ; find the sun's place in 
the ecliptic, bring it to the brass meridian, and set the index to 12. If 
the time be afternoon, turn the globe westward ; if in the forenoon, turn 
the globe eastward, till the index points to the given hour. The sur- 
face of the globe then represents the appearance of the heavens at that 
time and place. 

Problem 6. — To find the distance of Ihe Stars from each other, in 
degrees. 

Rule. — Lay the quadrant of altitude over any two stars, so that the 
division marked may be on one of the stars ; the degrees between 
them will show their distance, or the angle which these stars subtend, 
as seen from the earth. 

Example.— What is the distance, in degrees, between the two stars 
Vega and Altair 1 Ans. 34 degrees. 
Also, between Regulus and Procyon, 
" " Aldebaran and Sirius, 

" " Arcturus and Spica, 

" " Capella and the North Star ? 



78 



ILLUSTRATED ASTRONOMY 



1 



GLOSSARY, 



OR EXPLANATION OF ASTRONOMICAL TERMS, 



ABERRATION.— An apparent annual motion in the fixed stars, occasioned by the velocity of 
light combined with the real velocity of the earth in its orbit. 

Absorbent Media — Substances either solid, liquid, or fluid, which imbibe the rays of light and heat. 
Acceleration. — An increase in the rapidity of the motion of a moving body. The motions of the 
planets are accelerated from their aphelion to their perihelion. 
Acronycal. — A star is said to rise or to set acronycally when it rises or sets at the instant of sunset. 
JEriform. — Having the form of air. 
JErotite. — A meteoric stone. 

Air or Atmosphere.— A transparent, invisible, elastic fluid, surrounding the earth, in which we 
move and breathe. 
Altitude. — The height of an object above the horizon. 

Amphiscii. — A name applied to the inhabitants of the torrid zone, because within the year, their 
shadows, at noon, are cast both north and south. 

Amplitude. — The distance whicli a heavenly body rises from the east, or sets from the west point 
of the horizon 

Analemma. — A figure on the artificial globe, drawn from one tropic to the other, on which is 
marked the sun's declination for each day in the year. 

Angle. — The corner or opening between two lines that meet. A right angle contains 90 degrees, 
and is formed by one line falling perpendicularly upon another. An acute or sharp angle is less 
than a right angle. An obtuse or blunt angle is greater than a right angle. The measure of an 
angle is always an arc. 

Ans.le of Position of a Double Star. — The angle which a line joining the two stars makes with 
one parallel to the meridian. 

Angular Distance.— The distance between two objects, which is indicated by the angle, made by 
straight lines drawn to them from a given point. 

Annual Equation —A periodical inequality in the motion of the moon, or a planet, going through 
its changes in a year. 

Annual Revolution of the Earth. — Its yearly revolution round the sun. 
Annular. — Having the form of a ring. 

Anomaly.— The sun's angular distance from the apogee, or the earth's from aphelion. 
Antarctic Circle — A circle round the south pole, 23° 28' from it. 
Antipodes. — Those who live on directly opposite sides of the earth. 
Antatci. — Those who live in equal latitude on directly opposite sides of the equator. 
Aphelion. — The poim in a planet's orbit which is farthest from the sun. 
Apogee. — The point of the orbit of the moon or a planet farthest from the earth. 
Apparent Diameter — The diameter of a body as seen from the earth. 
Apparent Motion. — The motion of the heavenly bodies as viewed from the earth. 
Apparent Time. — The time shown by the sun, as indicated by a dial. 

Apsis. — The point of an orbit which is at the greatest or least distance from the centre ot motion. 
The former is called the higher apsis ; the latter the lower apsis. The two together are termed the 
apsides, and a line uniting them is called the apsis line, or line of the apsides. 
Aquarius. — The eleventh sign of the ecliptic. 
Arc. — Any part of the circumference of a circle. 
Arctic Circle — A circle round the north pole, 23° 28' from it. 

Areas. — In astronomy, they are the spaces passed over by the radius vector of a celestial body. 
Aries. — The first sign of the ecliptic. Its first point is at the vernal equinox. 
Argument. — A quantity by which another quantity or equation is found. 
Ascensional Difference. — The difference between right and oblique ascension. 
Aspect. — The appearance of the heavenly bodies with respect to position, angular distance, &c. 
Asteroids. — Eight small primary planets, whose orbits are between those of Mars and Jupiter. 
Their names are Vesta. Astrasa, Juno, Ceres, Pallas, Hebe, Iris and Flora. Some suppose them to 
be fragments of a planet, burst by some internal explosion. 

Astronomical Time. — Time reckoned from the noon of one day up to 24 hours, to the noon of 
the next day. It consequently is made up of the last 12 hours of the same civil day, and the first 
12 hours of the next civil day. 
Atmosphere. — The air that surrounds the earth. 
Attraction. — The power of one body to draw another towards it 
Austral. — Southern. 

Aurora. — The morning, or the morning twilight. 

Aurora Borealis, or Northern Lights. — A luminous appearance in the heavens, usually seen in 
high latitudes, and so named from its frequent resemblance to the morning dawn. 
Axis of Rotation. — The line around which a revolving body turns. 

Axis of an Ellipse. — The major axis is the greatest diameter. The minor axis is the least 
diameter. 

Azimuth. — The distance of a heavenly body east or west of the meridian, which is indicated by 
the angle between the meridian and the vertical circle passing through the body. 

Azimuth, or Vertical Circle — A great circle in the heavens, passing through the zenith and nadir, 
and cutting the horizon at right angles. 
Binary System of Stars. — Two stars revolving about each other. 
Bissextile, or Leap Year. — Every fourth year, in which February has 29 days. 
Body. — In astronomy this term is applied to any one of the celestial orbs. 
Calendar. — A term applied to the Almanac, or the divisions of time of which it treats. 
Calendar Months. — The months as laid down in the almanac. 
Cancer. — The fourth sign of the ecliptic. 
Capricorn. — The tenth sign of the ecliptic. 

Cardinal Points. — The east, west, north and south points of the horizon. 

Centrifugal Force. — The force which urges a revolving body forward in Its orbit, or tends to 
carry it away from the centre of motion. 

Centripetal force. — The force which draws a revolving body towards the centre of motion. 
Chord. — A straight line from one end of an arc to the other. 

Circle. — A figure bounded by a curve line, every part of which is equally distant from the cen- 
tre. A great circle is one whose plane divides a globe into two equal parts called hemispheres ; 
a small circle is one whose plane divides a globe into unequal parts. 

Circle of Decimation — The circle where the plane of the meridian meets the heavens. 
Circle of Illumination. — The circle that divides the enlightened from the dark hemisphere. 
Circumference. — The boundary of a circle. The circumference of every circle is supposed to be 
divided into 360 equal parts, called degrees ; each degree into 60 equal parts, called minutes ; and 
each minute into 60 equal parts, called seconds. 

Circumpolar Stars. — Those stars which revolve around the pole without passing below the 
horizon. 

Clouds. — Vapor, in the atmosphere, condensed into small drops of water, and thus rendered 
visible. 

Oolures — Those two meridians which pass through the equinoctial and solstitial points of the 
ecliptic, called the equinoctial and solstitial colures. 

Comet. — A body with a luminous train or tail, moving around the sun in a very elongated orbit. 
Complement of an Arc or Angle. — What it wants of 90 degrees. 
Concave. — Hollowing in a circular manner. 
Concentric Circles. — Circles having the same centre. 

Cone. — A solid with a circular base, and tapering equally upwards to a point. 
Conjunction. — Two heavenly bodies are in conjunction when they have the same longitude. A 
planet is in inferior conjunction when it is between the earth and sun ; in superior conjunction when 
jt is beyond the sun. The inferior planets only have inferior conjunction, but all have superior con- 
junction. 

Constellations. — Groups of stars to which the names of men and animals were anciently given. 
The whole starry firmament is divided into such groups. 



Convex. — Rounding out in a circular manner. 

Cosmical.— The rising or setting of a star is said to be cosmical, when it rises or sets at tne 
moment of sunrise. 

Cube. — A square solid of six equal sides. 

Culminate.— To pass the highest point of the diurnal are, which is at the meridian. 

Culmination. — The passing over the meridian, or point of highest altitude. 

Cycle. — A period of time in which the same phenomena or circumstances of a body begin to occur 
again in the same order. 

Cycle of the Moon. «>• Metonic Cycle. — A period of 19 years ; after which the changes of the moon 
return to the same days of the month (when five leap years are included,) as on the same year of 
the preceding cycle, or 19 years before. 

Cycle of the Sun.— A period of 2S years ; after which the same days of the month return to the 
same days of the week ; and the sun's place, to the same degrees and minutes of the ecliptic, as on 
the same year of the preceding cycle. 

Cycle of a Planet.— A period during which a planet passes through its various positions witn 
respect to the sun and earth. 

Cylinder. — A round figure or solid of equal size from end to end. 

Cylindrical. — Having the form ot a cylinder. 

Declination. — The angular distance of a heavenly body, north or south, from the equinoctial. 

Degree. — One 360lh part of the circumference of a circle. 

Diagonal. — A line drawn from corner to corner of a four sided figure. 

Dial. — An instrument showing the hour of the day, by the shadow of the sun. 

Diameter.— A straight line passing through the centre of a figure, and terminated both ways by 
its sides or surface. The longest and shortest diameters of an ellipse are called the transverse and 
conjugate diameters. 

Dichotomized.— Divided into equal and similar parts, as the disc of the moon at quadrature. 

Digit. — One-twelfth part of the apparent diameter of the sun or moon. 

Direct motion of a Planet. — Apparent motion from west to east, according to the order of the signs. 

Disc. — The apparent surface of a heavenly body. 

Diurnal Arc. — The arc described by a heavenly body from its rising to its setting. 

Diurnal Revolution of the Earth. — Its daily rotation on its axis, from west to east. 

Dominical Letter.— The letter in the calendar against Sunday ; the first 7 letters of the alphabet 
being applied to the first 7 days of the year. 

Dionysian Period. — A period of 532 years ; found by multiplying the cycles of the sun and moon. 

Earth — The globe on which we live. 

East. — The direction in which the sun rises at the equinoxes. 

Eccentric. — Deviating from the centre ; irregular. 

Ecccenlric Circles. — Those that are wholly or partially included in each other, but have different 
centres. 

Eccentricity. — The distance from the centre of an ellipse to eitherof its foci. 

Ecliptic. — The circle, where the plane of the earth's orbit meets the heavens. 

Egress. — The act of going out. 

Element. — Fundamental principle ; quantity by which something else is found. 

Elevation. — Height or altitude. 

Ellipse. — An oval ; a figure made by the oblique section of a cone. 

Elongation. — The angular distance of a planet from the sun, or the difference of their celestial 
longitude. 

Emersion. — The act of rising out of something, or re-appearing. 

Epact. — The age of the moon at the commencement of the year. 

Epicycle. — The curve described by a point of one circle, revolving upon another circle. 

Epoch or Era. — A particular time, from which events are reckoned 

Equation. — A quantity to be applied to mean time, place, or motion, in order to find the true. 

Euualor.— A great circle, whose plane is perpendicular to the earth's axis. 

Equinoctial or Celestial Equator. — The circle, where the plane of the equator meets the heavens. 

Equinoctial Points. — The points where the equinoctial cuts the ecliptic, or the first points of Aries 
and Libra. 

Equinox. — The time when the sun enters either of the equinoctial points. The vernal equinox 
occurs in March, the autumnal in September. 

Erection. — A periodic inequality in the motion of the moon. 

Firmament. — The heavens, or orb of fixed stars. 

Fixed Stars. — Those stars which preserve the same situation with respect to each other. 

Foci. — The plural of focus ; the two points round which an ellipse is drawn. 

Fogs or Mist. — Vapor, condensed into minute drops of water, as in clouds. 

Frustum. — What remains of a regular figure after a piece is cut oft' by a plane parallel to its base. 

Galaxy or Milky Way. — A luminous zone in the heavens, composed of an immense number of 
fixed stars 

Geocentric. — As seen from the earth, or the earth being the centre. 

Gibbous. — The shape of the illuminated part of the moon, when more than half and not the whole 
of its disc is visible. 

Globe. — A sphere, ball, or round body. Artificial globes of two kinds are made ; the terrestial, 
to represent the earth ; and the celestial, to represent the heavens. 

Golden Number. — The number of years in the cycle of the moon since the epact was nothing. 

Gravitation or Gravity. — The attraction or power w r hich draws all bodies towards each other. 
Also, its effect, as weight, caused by the earth's attraction. 

Hail. — Drops of rain, frozen while falling. 

Harvest Moon. — The full moon nearest the autumnal equinox. 

Heliacal. — The heliacal rising or setting of a star takes place, when it rises a little before or sets 
a little after the sun. 

Heliocentric. — As seen from the sun, or the sun being the centre. 

Hemisphere. — Half a sphere or globe. 

Heteroscii. — A name given to the inhabitants of the two temperate zones, because at noon those 
in the northern always have their shadows in an opposite direction to those in the southern. 

Horizon — The visible or sensible horizon is the circle where the sky and earth appear to meet. 
The rational horizon is parallel to the visible, and its plane divides the earth into upper and lower 
hemispheres. It is represented on the artificial globe by the wooden horizon. The circle where 
its plane meets the heavens is cailed the celestial horizon. 

Horizontal. — Level or parallel to the horizon. 

Hour Circle. — A small circle, on the globe, near the north pole, having on it the hours of the day. 

Immersion. — The act of plunging into something, or disappearing. 

Inclination. — Angle. A position forming an acute angle. 

Index. — A movable hand on the globe, to point out the time on the hour circle. 

Ingress. — An entrance. 

Intercalation. — The insertion of an extra day in the calendar, as the Bissextile. 

Julian Period. — A period of 7.9S0 years, found by multiplying together the cycles of til" 1 sun nnd 
moon, and the Roman Indiction. 

Julian Year. — A period of exactly 365{ days. 

Latitude on the Earth. — The distance of a place north or south of the equator. 

Latitude in the Heavens. — The angular distance of a heavenly body from the ecliptic. 

Leap Year. — Every fourth year, in which an extra day is added to the calendar. 

Leo. — The fifth sign of the ecliptic. 

Libra. — The 7th sign of the ecliptic. 

Libration of the Moon. — A periodical oscillation of her disc. 

Limb. — The curved edge of the sun or moon's disc. 

Line. — That which has length but no breadth. 

Longitude on the Earth. — Distance east or west of the first meridian. 



ILLUSTRATED ASTRONOMY 



70 



GLOSSARY, OR EXPLANATION OF ASTRONOMICAL TERMS, (continued.) 



Longitude in the Heavens. — The angular distance of a heavenly body, measured on the ecliptic 
eastward, from the first point of Aries. 

Luminous. — Capable of shining without light from another body. 

Lunar Distance.— The angular distance ot the centre of a celestial object from the centre of the 
moon. 

Lunar Month. — The time from one new moon to the next. 

Lunation. — The average time of the lunar month. 

Manner's Compass. — An instrument with a magnetic needle, to point out the horizontal 
direction. 

Mass. — The quantity of matter in a body. 

Mean. — Average ; applied to distance, longitude, motion, place, time, fee. 

Meridian of a Place. — A great circle passing through the place and tiic poles of the earth. The 
first meridian is the one from which longitude is reckoned. The brazen meridian is that in which 
the artificial globe turns. 

Meteor. — A transitory object in the air. Falling stones are often called meteorites. 

Minute. — One 60th part of a degree ; also one 60th part of an hour. 

Moon's Southing. — The time when the moon comes to the meridian of a place. 

Nadir. — A point directly opposite to the zenith, or beyond the centre ol the earth. 

Neap Tide. — The least flood and ebb tide. 

Nebula. — C'lus^rs of Stars, or other causes of the luminous appearances in the heavens. 

Nocturnal Arc. The arc described by a heavenly body from its setting to its rising. 

Nonagesimal Decree. — The highest point of the ecliptic above the horizon. 

Node — The point of the moon's or a planet's orbit that is cut by the plane of the ecliptic. There 
are two nodes, one on each side of the centre of motion ; and a line joining them is called the line 
of the nodes. The place where the body passes to the north of the ecliptic is called the ascending 
node j the other the descending node. 

New Style. — The reckoning of time established by Gregory XII h, and now generally adopted. 

North. — That point of the horizon which is directly towards the northern pole. 

Nucleus of a Comet. — The uart of its head which appears to be dense. 

Nutation — A variation in the direction of the earth's axis, caused by the attraction of the moon 
on the protuberant matter at the terrestrial equator. 

Oblique.- -Forming an acute or obtuse angle ; not perpendicular. 

Oblique Ascension. — That degree of the equinoctial which rises with a body in an oblique 
sphere. 

Oblique Descension. — That degree of the equinoctial which sets with a body in an oblique 
sphere. 

Obliquity. — Deviation from parallelism and from perpendicularity. 

Obliquity of the Ecliptic. — The angle formed by the equinoctial with the plane of the ecliptic. 

Occidental. — To the west, where the heavenly bodies appear to descend. 

Occultation. — The eclipse of a star or planet by the moon or by another planet. 

Octant. — Forty-five degrees distant, or the eighth part of a circle. 

Old Style. — That reckoning of time which makes every fourth year a leap year. 

Opake. — Not luminous or transparent. 

Opposition. — Two bodies are in opposition when they are on opposite sides of the earth. 

Orbit. — The path in which one body moves round another. 

Oriental. — Towards the east, where the heavenly bodies rise. 

Parallax.— The difference of the place of a body, as seen from different points of view. Diurnal 
parallax is the difference between the apparent and true place of a body. Horizontal parallax is 
the diurnal parallax of a body in the horizon. Annual parallax is the difference of the apparent 
place of a body, as seen from different parts of the earth's orbit. 

Parallactic Motion. — Angular motion sufficiently great to be perceived. 

Parallel Lines. — Those continued in the same direction, at the same distance from each other. 
Parallels of altitude, declination, and latitude, are small circles parallel to the horizon, equinoctial, 
and equator. 

Penumbra. — A partial or imperfeet shadow. 

Perigee. — The point nearest the earth, in the orbit of the moon or a planet. 

Perioeci. — Those who live in equal latitude on opposite sides of the pole. 

Perihelion. — The lower apsis, or point nearest the sun, in a planet's orbit. 

Periodic Inequality.— An irregularity in the motion of a celestial body, requiring a comparatively 
short time for its accomplishment. 

Periodic Time. — The time in which a heavenly body revolves around its centre of motion. 

Periscii.—A name given to the inhabitants of the frigid zone, because their shadows turn all 
round them in one day 

Perpendicular. — Making a right angle with some line or surface. 

Perturbations. — Irregularities in the motions of bodies, from some disturbing cause. 

Phases. — Different appearances of the moon and planets as they are differently illuminated. 

Phenomena. — Appearances in the works of nature. (Singular Phenomenon.) ' 

Physical. — Belonging to material nature. 

Pisces. — The 12th sign of the ecliptic. 

Plane. — Length and breadth without thickness. The plane of a circle is the surface contained 
within it, and continued out of it on all sides, indefinitely, to the heavens. 

Planet.— An opake body revolving around the sun. The secondary planets revolve around the 
primary planets, as well as around the sun. Those planets nearer to the sun than the earth is, are 
called inferior ; those more distant are called superior. 

Pleiades. — The seven stars in the constellation Taurus. 

Point. — That which has position but no magnitude. 

Polar Circles. — Small circles drawn around the poles, 23J degrees from them. 

Polar Distance. — Angular distance from the pole, measured on a circle of declination. 

Poles.— The terrestrial poles are the extremities of the earth's axis. The celestial poles are the 
points where the earth's axis, if produced, would meet the heavens. 

Pole Star. — A star of the second magnitude, near the north pole of the heavens. 

Pointers. — Two stars in the great bear, that serve to point out the pole star. 

Precession of the Equinoxes. — A retrograde motion, on the ecliptic, of the equinoctial points, 
caused by the action of the sun and moon upon the protuberant matter at the earth's equator. 

Quadrant.— Ninety degrees, or a quarter of a circle. An instrument to measure angles. 

Quadrature. — The position, a quarter of a circle from the sun. 

Quadrilateral Figure. — One that has four sides. 

Quartile. — Ninety degrees distant from each other. 

Quiescent. — At rest ; not in motion. 

Radiation. — An emission of rays. 

Radius. — A straight line from the centre of a circle or sphere to its circumference. 

Radius Vector. — A straight line between a planet and the sun, or centre of motion. 

Rain. — Drops of -/ater falling from the clouds. 

Reflection.— The turning back of rays of light or sound from a surface. 

Refraction.— The breaking or bending of a ray of light in passing through media of different 
densities 

Repulsion. — The property by which bodies recede or fly from each other. 

Retrograde Motion of a Planet. — Apparent motion from east to west, contrary to the order of the 
signs. 

Revolution. — Motion from a point round to the same again. 

Right Ascension— The distance east on the equinoctial from the first point of Aries. 

Right Line. — A straight line ; a direct course. 

Roman Indiction. — A period of 15 years. 

Rotation. — The motion of a body round its axis 



Satellite — A moon, or secondary planet. 

Scorpio. — The eighth sign of the ecliptic. 

Secondary Circles. — Such as are in planes that are perpendicular to those circles of which they 
are the secondaries. 

Sector of a Circle.— Space enclosed by two radii and an are, less than a semicircle. 

Secular Inequalities. — Variations in the motions of the heavenly bodies, requiring many ages for 
their accomplishment. 

Segment. — Any part of the surface of a circle cut off'by a cord. 

Semicircle. — Half a circle. Half of the circumference, or an arc of ISO degrees 

Sidereal Day. — The time included between two consecutive transits of the same star at the same 
meridian. This period is invariably of exactly the same continuance ; and it is the only one in 
nature, with which we are acquainted, that is so. Hence it forms a perfect standard measure, by 
reference to which all portions of time may be ascertained. Astronomical clocks are made to 
show sidereal time. It may likewise be observed that our standard measures of length, capacity, 
and weight, depend upon the equable rotation of the earth on its axis, as they are referred to the 
length of a pendulum beating seconds of mean lime. 

Sign.— Thirty degrees, or the 12th part of a circle. The ascending signs of the ecliptic are those 
in which the sun's meridian altitude is daily increasing. 

Snow. — Water frozen while in the form of clouds, mist, or fine rain, which then falls gently to 
the earth. 

Solar Day. — The time from one noon to the next, is the apparent, and the average time of that 
period, the mean, solar day. 

Solar System. — The sun, with its planets and comets arranged regularly, in their several positions. 

Solstices. — The times at which the sun is in the solstitial points. When the sun is at the summer 
solstice all places in the northern hemisphere have their longest day. These days vary in lem'th 
from 12 hours at the equator to 24 at the arctic circle, and in the frigid zone they increase from"24 
hours at the arctic circle to 6 months at the pole, where there is but one day and night durin" - the 
year. At the same time all places in the southern hemisphere have their shortest day, These°'ary 
from 12 hours at the equator to nothing at the antarctic circle, where the sun does" not rise above 
the horizon. The length of the days in south latitude corresponds to the length of the nights in 
north latitude ; and the length of the nights in south latitude corresponds to the length of the days 
in north latitude. When the sun is at the winter solstice, this condition of things is reversed, and 
the southern hemisphere presents the same phenomena, with respect to the sun, as does the north- 
ern wdien the sun is at the summer solstice. 

Solstitial Points. — The points of the ecliptic which are farthest from the equinoctial. 

South. — That point of the horizon which is directly opposite to the north pole. 

Sphere.— A globe or ball. A solid which has eiery point of its surface equally distant from its 
centre. Also, the concave expanse of the heavens that surrounds the earth. The sphere has three 
positions, right, oblique and parallel. Those who live at the equator have a right sphere, all the 
circles of daily motion rising directly above, and descending directly below the horizon.' Those 
who live between the equator and poles have an oblique sphere, all the circles of daily motion 
being oblique to the horizon. Were any one at either of the poles he would have a parallel sphere, 
all the circles of daily motion being parallel to the horizon. On the artificial globe a right sphere 
is represented by placing both poles in the horizon ; an oblique sphere by raising one pole a little 
and depressing the other ; a parallel sphere, by bringing one pole to the zenith and the other to the 
nadir. 

Spherical — Having the form of a sphere. 

Spheroid.— A solid resembling a sphere. If the polar diameter be the least, it is called an oblate 
spheroid ; if it be the greatest, it is called a prolate or oblong spheroid. 

Spring Tide. — The greatest flood and ebb tide. 

Stationary, — A term applied to the apparent motion of a planet, when its real motion, combined 
with that of the earth, causes it to remain at the same point in the heavens. 

Supplement of an arc or angle. — What the arc or angle wants of 180 degrees. 

Surface. — That which has length and breadth, hut no thickness. 

Synodic Month. — A complete lunation, or from one new moon to another; it bein"" 29 days 12 
hours and 44 minutes. 

Syzygies. — The points in the moon's orbit where she is new or full. 

Taurus. — The second sign of the ecliptic. 

Tide.— The rising and falling of the waters of the ocean. The rising of the water is called flood 
tide ; the falling, ebb tida. 

Transit. — The passage of a body across the meridian of a place. The transit of Mercurv and 
Venus usually means their apparent passage across the sun's disc. 

Trapezium. — A figure bounded by four unequal sides. 

Triangle.— A figure bounded by three lines, or sides. An equilateral triangle has three equal 
sides ; an isosceles, only two ; a scalene triangle has three unequal sides. A triangle is called a 
right, obtuse, or acute angled triangle, according as it has a right, obtuse, or three acute angles. 

Tropic of Cancer. — A small circle, 23 p US' north of the equator, and parallel to it. 

Tropic if Capricorn. — A small circle, 23" 2S' south of the equator, and parallel to it. 

Tropical Year. — The period between the consecutive returns of the sun to the same tropic or 
solstice. 

True Distance. — The actual distance of a body from the sun, or of a satellite from its planet. 

True Place of a Planet. — The place where it would appear to be, if seen from the centre of the 
earth, or centre of motion. 

Twilight. — The faint light of the sun before sunrise and after sun-set. 

Umbra. — A dark or total shadow. 

Universe — The whole material creation. It has beGn improperly applied sometimes to large 
clusters of stars. 

Vapor. — Water in an teriform state — steam. 

Vertex. — The head, top, or summit. 

Vertical. — The direction of the plumb-line. 

Vertical Plane — A plane passing through the plumb-line, consequently perpendicular to the 
horizon 

Vertical Circle. — A circle in a vertical plane, passing through the zenith and nadir, and cutting 
the horizon at right angles. 

Virgs. — The 6th sign of the ecliptic. 

Waning. — Declining in power, or decreasing in light. 

West. — That direction in which the sun sets when in the equinoxes. 

Wind. — Air in motion. The trade winds blow steadily to the westward, in the Atlantic and 
Pacific oceans, between the tropics. The monsoons, or shifting trade winds, in the Indian oceaii, 
blow part of the year oneway, and the other part in an opposite direction. The winds beyond 
the 40th degree of latitude are all variable. In the torrid zone, near the sea, breezes blow from the 
land in the morning and from the sea in the evening. 

Year. — A solar or tropical year is the period from the departure of the sun from the summer sol- 
stice, to its return to it again. Its length is 365 days, 6 hours, and nearly 49 minutes. The sidereal 
year, which is the period between the departure and return of the sun to a fixed star, is about 17 
minutes longer. The anomalistical year is the time from the sun's leaving his apogee till he 
returns to it, and is 365 days, 6 hours, and about 14 minutes. 

Zenith — The point in the heavens directly over head. 

Zenith Distance. — The angular distance of a heavenly bod_ from the zenith, measured on a verti- 
cal circle. 

Zodiac. — A space or belt in the heavens, 16 degrees broad, , ° on each side of the ecliptic,) in 
which are the orbits of all the planets except a part of the asteroids. 

Zone. — A belt or girdle on the earth's surface, formed by circles parallel to the equator There 
are five zones ; the torrid, two temperate, and two frigid, formed by the tropics and polar circles 



TOWER'S SERIES OF SCHOOL BOOKS, 

PUBLISHED BY 

DANIEL BURGESS, &, CO. 60 JOHN-STREET, NEW YORK. 



Gradual Primer. First Book. 

The merits of this book consist, — 

1. In coupling letters by their resemblances. 

2. In giving only a few letters of the alphabet, before words are given com- 
posed solely of those few letters. 

3. In giving only one vowel in a lesson, with words which contain the name- 
sound of that vowel. This is a new and peculiar method of teaching the alphabet. 

4. In considering the several powers of each vowel in a separate, lesson, with 
easy words, and short, plain sentences, to illustrate each individual power or 
sound ; thus teaching only one thing at a time. 

5. The diphthongs or combined vowels are taught in the same manner. 

6. Each consonant element is then considered by itself, in a separate les- 
son, with easy words and sentences, for exercise on its particular sound. 

7. Particular and specific directions are, for the first time, given to teach- 
ers, for uttering each elementary sound in the language. 

8. More general directions or suggestions are also given for teachers. 
Tables, peculiar to this Series alone, are inserted for daily practice of classes 

simultaneously in all the simple elementary sounds. 

These are the prominent features of this Primer, and are peculiar to it alone. 
The teacher, as well as the pupil, will, from its use, lay the foundation of a 
distinct articulation, and be saved from much expense of time and labor in 
unlearning. This is "the right step taken in the right place." 
Introduction to the Gradual Reader. Second Book. 

The peculiarities of this book consist, — 

1. In taking the pupil gradually through all the easier consonant com- 
binations, by a regular progressive exercise on each combination. 

2. Through all the points, or marks used by writers, illustrating each in a 
separate lesson. 

3. Through all the simple slides of the voice, in the same manner. 

4. Progressive reading lessons, adapted to the progress of the pupil. — The 
reading lessons are kept entirely distinct from the lessons in articulation, points, 
&c, that only one thing may be taught at a time, as in the Primer, which it 
is designed to follow. 

5. Tables for daily simultaneous practice of the elementary sounds, and sim- 
ple combinations. This book is the second progressive step in attaining a dis- 
tinct utterance, and correct pronunciation. 

6. Suggestions to teachers for avoiding errors in reading. 

Gradual Reader. Third Book. 

This book contains, — 

1. Such a selection of reading matter as will interest, as well as instruct, the 
learner, progressively suited to his capacity. 

2. A complete and original system of articulation, consisting of exercises 
upon every vowel and consonant element, and upon every vowel and consonant 
combination, in the language, even the most difficult. This was the first ever 
published, and is the only completesystem. 

3. Tables for simultaneous practice, by a whole school, on all the elemen- 
tary sounds and their combinations. Since the publication of these Exercises, 
in 1841, the subject of articulation has received much attention, and they are 
said to have done more, for both teacher and pupil, in making good readers, 
than any other book. 

4. The Gradual Reader was prepared as stated in the preface, on the plan of teach- 
ing only one thing at a time, a plan peculiar to this book, unless copied by others. 

5. The exercises are kept separate from the reading lessons, that the whole 
school at. once, may be kept daily drilled in some portion of them previous to read- 
ing ; then the pupil's attention will not be continually called from the sentiment 
and expression of a piece, by constant interruption, to correct his articulation. 

6. The exercises in this book are full, to supply any deficiency in the elemen- 
tary instruction of advanced pupils. (See printed notices of the book and system.) 

These three books furnish complete and thorough instruction in articulation, 
the groundwork of all good reading. 

N. A. Second Class Reader. Fourth Book. 

1. This Reader contains an elaborate but comprehensive treatise on Elocu- 
tion, in which the leading principles of good reading are simplified, and rules 
deduced and illustrated by practical examples. These are so plain that the 
child can easily comprehend them. 

2. References are made in each reading lesson to some of the principles al- 
ready developed, that the pupil may exercise his mind by the practical appli- 
cation of the same. 

3. Each lesson has its partial vocabulary, to exercise the pupil's judgment in 
discriminating and selecting the definition appropriate to explain the author's 
meaning. 

4. Above a thousand of the most difficult words are thus practically learn- 
ed ; and the pupil's knowledge of language is understanding^ enlarged. 

5. Each lesson is preceded by practical exercises in enunciation, exhibit- 
ing the correct pronunciation of words, and the distinct utterance of simple 
elements and difficult combiL itions. 

6. These exercises may ' e practised simultaneously previous to taking up 
the reading lesson. 

7. The selections have been carefully made in reference to their practical 
utility and interest, and their adaptation to the capacity of the pupils for whom 
they were designed. 

N. A. First Class Reader. Fifth Book. 

This Reader contains a philosophical treatise on the higher departments 



of Elocution. In this treatise the vocal elements are treated as the constit- 
uents of speech. Each one is considered in an insulated light, and illustrated 
by appropriate exercises. It is next shown how these constituents are applied 
in combination, in every instance of chaste and impassioned eloquence or cor- 
correct and impressive reading. When this treatise is examined, it will be found 
that the whole subject is clearly illustrated, and the essential points are arrang- 
ed in such a manner as to be easily comprehended. " It is my firm conviction/' 
says one of the most accomplished scholars of the present day, "the treatise 
on elocution and principles of reading as illustrated and explained in the North 
American First and Second Class Readers, will do more to excite the atten- 
tion on the subject of language and reading, than any thing else which has yet 
made its appearance ; and were I again to teach, I should by all means exercise 
my classes on the illustrations as they are arranged under each principle. The 
selections are excellent, and, if merit be recommendation or any criterion 
of success, these books are destined to be more extensively used than any other 
series of reading books which has yet been published." These books are now 
presented to the public without agents to push them into notice, it being pre-' 
sumed that when examined they will meet with general faTor. 

Gradual Speller. 

1. This book is the first attempt to arrange words, in separate classes, by the 
consonant combinations — thus aiding the memory on the princi pie of association. 

2. It is free from the unmeaning cuts which disfigure most books of the kind, 
and furnish a gratuitous supply of playthings to distract the attention. 

3. It is not cumbered with reading lessons, useless, because out of place. 

4. It contains an exercise on each consonant element as well as each vowel 
element. 

5. It gives also an exercise on each consonant combination separately. No 
other spelling-book does. 

6. It gives the sound of each vowel in every word ; without which, any Spel- 
ling-book would be worse than useless in a school. 

7. The sowids of the vowels are indicated by a new method ; so simple, that 
any child can readily master and use it. 

8. The same notation answers for the diphthongs, which is an advantage 
over any other plan. 

9. As each element and each combination is considered in a separate exer- 
cise, the book is a great collateral aid to articulation, while it gives the correct 
pronunciation in connection with teaching the orthography of the language. 

Intellectual Algebra. 
This is on a new and original plan, and is the first attempt to simplify and 
illustrate this science, that it may be taught orally. As a discipline of the mind 
in teaching the pupil to think and reason, algebra is pre-eminent; and this 
work places it in the power of younger classes to be benefited by such mental 
exercise. Where it has been used, it has more than answered the high ex- 
pectations of teachers. 

1. The processes are so divided and subdivided as to present but one thing 
at a time to the learner, and that in its simplest form. 

2. The operations are limited to small numbers, so as not to embarrass the 
reasoning powers. 

3. The pupil is led gradually from the simplest to more complicated reasoning. 

4. Though not designed for that purpose, it has been used successfully as a 
text-book for written algebra, 

A Complete Key to the Algebra. 

This book contains explanations and solutions to all the questions in the 
Algebra, for the convenience of teachers, and for their use only. 

Gradual Lessons in Grammar. 

1. It is based entirely on the analysis and composition of sentences ; and 
its exercises are, consequently, from the very beginning, entirely of a practi- 
cal character. 

2. The subject and the predicate of each proposition are foci modified or 
limited by all other words therein. 

3. The pupil must not only know the meaning of each word, but how it 
affects the meaning of the general proposition. 

4. Besides the abstract power of words, the local value will also be gradually 
acquired from observing their modified influences as they are variously used. 

5. Language is, in this way, both regarded and studied as the medium of 
thought. 

6. The two principal parts of a proposition must first be found ; then how 
each is modified by the several words that cluster around it ; and thus how the 
meaning of the part or the whole is affected thereby. This is an invaluable 
exercise of the understanding. 

7. Then the pupil is required to analyze compound sentences, till the con- 
nection or dependence of clauses is rightly understood, with their limiting 
or modifying power. 

8. Sentences are thus analyzed and constructed, and the relations of words 
and clauses comprehended, with the limiting force of each, before the minor 
distinctions and the technicalities are introduced. 

9. The plan is new, and pleases every enlightened teacher who examines 
it. The pupil is taught to tompose as well as analyze. 

Teachers say that this Grammar opens a new path for the pupil, enabling him, 
to pursue this sometimes dry study not only understandingly, but with interest 
and pleasure. It is predicted of the " Lessons," that they will produce as great a 
change in the method of teaching grammar, as Colburn's " First Lessons" did 
in arithmetic. 

5 



POPULAR AND YALUABLE SCHOOL 



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ikiiaj 



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ACKERMAN'S NATURAL HISTORY, 

288 pages, 12mo., half bound .... 

AMERICAN EXPOSITOR, 

or, Intellectual Definer. — by R. Claggett, A. M. - 

ELOCUTION MADE EASY, 
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450 pages, 12mo., half bound, ... 

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BY R. C. SMITH, A. M. 

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or, First Book in Arithmetic, 18mo. 
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Walker, 432 pages, 12mo., sheep. 



GRADUAL LESSONS IN ENGLISH GRAMMAR, 

with Sequel— by D. B. Tower and Benj. F. Tweed, 288 
p;.ges, 12mo. ...... 

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or, Oral Exercises in Alegbra — for Common Schools, by 

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" « t, « « u <t c I th. 

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THE MOZART COLLECTION OF SACRED MUSIC, 

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of Teaching the Rudiments of Music. — by E. Ives, Jr. 
THE MUSICAL READER, 

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